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COVER PAGE - shares	9 Months Ended
COVER PAGE - shares	Sep. 30, 2019	Oct. 15, 2019
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	CASELLA WASTE SYSTEMS, INC.
Entity File Number	000-23211
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0000911177
Entity Incorporation, State or Country Code	DE
Entity Filer Category	Large Accelerated Filer
Title of 12(b) Security	Class A common stock, $0.01 par value per share
Trading Symbol	CWST
Security Exchange Name	NASDAQ
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Tax Identification Number	03-0338873
Entity Address, Address Line One	25 Greens Hill Lane,
Entity Address, City or Town	Rutland,
Entity Address, State or Province	VT
Entity Address, Postal Zip Code	05701
City Area Code	802
Local Phone Number	775-0325
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		46,792,758
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 5,028	$ 4,007
Accounts receivable, net of allowance for doubtful accounts of $1,478 and $931, respectively	89,882	74,937
Refundable income taxes	2,789	2,254
Prepaid expenses	8,423	7,345
Inventory	6,976	6,542
Other current assets	693	2,008
Total current assets	113,791	97,093
Property, plant and equipment, net of accumulated depreciation and amortization of $831,950 and $878,701, respectively	434,081	404,577
Operating lease right-of-use assets	109,604
Goodwill	184,295	162,734
Intangible assets, net	60,983	34,767
Restricted assets	1,410	1,248
Cost method investments	11,264	11,264
Deferred income taxes	8,840	9,594
Other non-current assets	11,512	11,133
Total assets	935,780	732,410
CURRENT LIABILITIES:
Current maturities of long-term debt and finance leases	3,571	2,298
Current operating lease liabilities	9,582
Accounts payable	59,370	57,289
Accrued payroll and related expenses	10,116	10,969
Accrued interest	2,340	2,415
Contract liabilities	2,812	3,074
Current accrued capping, closure and post-closure costs	8,527	11,633
Other accrued liabilities	30,641	23,819
Total current liabilities	126,959	111,497
Long-term debt and finance leases, less current portion	523,975	542,001
Operating lease liabilities, less current portion	71,910
Accrued capping, closure and post-closure costs, less current portion	64,092	61,442
Deferred income taxes	2,637	2,519
Other long-term liabilities	35,395	30,783
COMMITMENTS AND CONTINGENCIES
Casella Waste Systems, Inc. stockholders' equity (deficit)
Additional paid-in capital	482,987	373,716
Accumulated deficit	(366,082)	(388,669)
Accumulated other comprehensive loss	(6,571)	(1,308)
Total stockholders' equity (deficit)	110,812	(15,832)
Total liabilities and stockholders' equity (deficit)	935,780	732,410
Class A Common Stock
Casella Waste Systems, Inc. stockholders' equity (deficit)
Common stock	468	419
Class B Common Stock
Casella Waste Systems, Inc. stockholders' equity (deficit)
Common stock	$ 10	$ 10

CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	9 Months Ended	12 Months Ended
CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	Sep. 30, 2019 USD ($) vote $ / shares shares	Dec. 31, 2018 USD ($) vote $ / shares shares
Statement of Financial Position [Abstract]
Accounts receivable - trade, allowance for doubtful accounts \| $	$ 1,478	$ 931
Accumulated depreciation and amortization \| $	$ 831,950	$ 878,701
Class A Common Stock
Common stock, par value (in dollars per share) \| $ / shares	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	46,792,000	41,944,000
Common stock, shares outstanding	46,792,000	41,944,000
Class B Common Stock
Common stock, par value (in dollars per share) \| $ / shares	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000	1,000,000
Common stock, shares issued	988,000	988,000
Common stock, shares outstanding	988,000	988,000
Votes per share held \| vote	10	10

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 198,547	$ 172,832	$ 549,670	$ 485,936
Operating expenses:
Cost of operations	131,273	114,118	377,707	331,527
General and administration	22,536	20,545	67,423	62,365
Depreciation and amortization	20,940	18,202	58,144	51,572
Withdrawal costs - multiemployer pension plan	3,591	0	3,591	0
Expense from acquisition activities and other items	1,097	581	2,237	930
Southbridge landfill closure charge (settlement), net	625	(9,498)	2,097	(7,740)
Contract settlement charge	0	0	0	2,100
Development project charge	0	0	0	311
Total operating expenses	180,062	143,948	511,199	441,065
Operating income	18,485	28,884	38,471	44,871
Other expense (income):
Interest income	(66)	(53)	(287)	(161)
Interest expense	6,235	6,424	18,849	19,347
Loss on debt extinguishment	0	0	0	7,352
Other income	(248)	(166)	(960)	(597)
Other expense, net	5,921	6,205	17,602	25,941
Income before income taxes	12,564	22,679	20,869	18,930
Provision (benefit) for income taxes	178	377	(1,718)	(1,166)
Net income	$ 12,386	$ 22,302	$ 22,587	$ 20,096
Basic earnings per share attributable to common stockholders:
Weighted average common shares outstanding	47,690	42,779	47,029	42,605
Basic earnings per common share (in dollars per share)	$ 0.26	$ 0.52	$ 0.48	$ 0.47
Diluted earnings per share attributable to common stockholders:
Weighted average common shares outstanding	48,361	44,175	47,660	43,938
Diluted earnings per common share (in dollars per share)	$ 0.26	$ 0.50	$ 0.47	$ 0.46

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 12,386	$ 22,302	$ 22,587	$ 20,096
Hedging activity:
Interest rate swap settlements	(120)	(147)	(187)	(217)
Interest rate swap amounts reclassified into interest expense	147	156	216	247
Unrealized (loss) gain resulting from changes in fair value of derivative instruments	(774)	863	(5,292)	1,503
Other comprehensive (loss) income	(747)	872	(5,263)	1,533
Income tax provision related to items of other comprehensive (loss) income	0	235	0	413
Other comprehensive (loss) income, net of tax	(747)	637	(5,263)	1,120
Comprehensive income	$ 11,639	$ 22,939	$ 17,324	$ 21,216

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Additional Paid-In Capital	Accumulated Deficit	Accumulated other comprehensive loss	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
Beginning balance at Dec. 31, 2017	$ (37,862)	$ 356,638	$ (395,107)	$ 184		$ 413		$ 10
Beginning balance (in shares) at Dec. 31, 2017						41,298		988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	310	306				$ 4
Issuance of Class A common stock (in shares)						402
Stock-based compensation	2,077	2,077
Net income	(3,910)		(3,910)
Hedging activity	568			568
Ending balance at Mar. 31, 2018	(38,817)	359,021	(398,999)	734		$ 417		$ 10
Ending balance (in shares) at Mar. 31, 2018						41,700		988
Beginning balance at Dec. 31, 2017	(37,862)	356,638	(395,107)	184		$ 413		$ 10
Beginning balance (in shares) at Dec. 31, 2017						41,298		988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,096
Hedging activity	1,120
Ending balance at Sep. 30, 2018	(5,279)	367,999	(374,993)	1,286		$ 419		$ 10
Ending balance (in shares) at Sep. 30, 2018					41,932	41,932	988	988
Beginning balance at Mar. 31, 2018	(38,817)	359,021	(398,999)	734		$ 417		$ 10
Beginning balance (in shares) at Mar. 31, 2018						41,700		988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	361	360				$ 1
Issuance of Class A common stock (in shares)						65
Stock-based compensation	2,121	2,121
Net income	1,704		1,704
Hedging activity	(85)			(85)
Ending balance at Jun. 30, 2018	(34,716)	361,502	(397,295)	649		$ 418		$ 10
Ending balance (in shares) at Jun. 30, 2018						41,765		988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock - acquisition	4,258	4,257				$ 1
Issuance of Class A common stock - acquisition (in shares)						150
Issuances of Class A common stock	72	72
Issuance of Class A common stock (in shares)						17
Stock-based compensation	2,168	2,168
Net income	22,302		22,302
Hedging activity	637			637
Ending balance at Sep. 30, 2018	(5,279)	367,999	(374,993)	1,286		$ 419		$ 10
Ending balance (in shares) at Sep. 30, 2018					41,932	41,932	988	988
Beginning balance at Dec. 31, 2018	(15,832)	373,716	(388,669)	(1,308)		$ 419		$ 10
Beginning balance (in shares) at Dec. 31, 2018					41,944	41,944	988	988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock - equity offering	100,446	100,410				$ 36
Issuance of Class A common stock - equity offering (in shares)						3,565
Issuance of Class A common stock - acquisition	0	(1)				$ 1
Issuance of Class A common stock - acquisition (in shares)						67
Issuances of Class A common stock	260	253				$ 7
Issuance of Class A common stock (in shares)						676
Stock-based compensation	1,431	1,431
Net income	(1,714)		(1,714)
Hedging activity	(1,557)			(1,557)
Ending balance at Mar. 31, 2019	83,034	475,809	(390,383)	(2,865)		$ 463		$ 10
Ending balance (in shares) at Mar. 31, 2019						46,252		988
Beginning balance at Dec. 31, 2018	(15,832)	373,716	(388,669)	(1,308)		$ 419		$ 10
Beginning balance (in shares) at Dec. 31, 2018					41,944	41,944	988	988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,587
Hedging activity	(5,263)
Ending balance at Sep. 30, 2019	110,812	482,987	(366,082)	(6,571)		$ 468		$ 10
Ending balance (in shares) at Sep. 30, 2019					46,792	46,792	988	988
Beginning balance at Mar. 31, 2019	83,034	475,809	(390,383)	(2,865)		$ 463		$ 10
Beginning balance (in shares) at Mar. 31, 2019						46,252		988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	2,318	2,315				$ 3
Issuance of Class A common stock (in shares)						347
Stock-based compensation	1,889	1,889
Net income	11,915		11,915
Hedging activity	(2,959)			(2,959)
Ending balance at Jun. 30, 2019	96,197	480,013	(378,468)	(5,824)		$ 466		$ 10
Ending balance (in shares) at Jun. 30, 2019						46,599		988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	1,078	1,076				$ 2
Issuance of Class A common stock (in shares)						193
Stock-based compensation	1,898	1,898
Net income	12,386		12,386
Hedging activity	(747)			(747)
Ending balance at Sep. 30, 2019	$ 110,812	$ 482,987	$ (366,082)	$ (6,571)		$ 468		$ 10
Ending balance (in shares) at Sep. 30, 2019					46,792	46,792	988	988

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 22,587	$ 20,096
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	58,144	51,572
Operating lease right-of-use assets expense	7,272
Depletion of landfill operating lease obligations		7,827
Interest accretion on landfill and environmental remediation liabilities	5,310	4,291
Amortization of debt issuance costs and discount on long-term debt	1,724	1,875
Stock-based compensation	5,218	6,366
Gain on sale of property and equipment	(806)	(414)
Southbridge Landfill non-cash closure charge	58	1,354
Southbridge Landfill insurance recovery for investing activities	0	(3,506)
Development project charge	0	311
Non-cash expense from acquisition activities and other items	71	211
Loss on debt extinguishment	0	7,352
Withdrawal costs - multiemployer pension plan	3,591	0
Deferred income taxes	(1,267)	79
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(15,141)	(12,161)
Landfill operating lease contract expenditures	(3,197)	0
Accounts payable	1,634	8,009
Prepaid expenses, inventories and other assets	(1,297)	829
Accrued expenses, contract liabilities and other liabilities	(17,986)	(4,174)
Net cash provided by operating activities	71,495	89,917
Cash Flows from Investing Activities:
Acquisitions, net of cash acquired	(73,496)	(58,176)
Additions to property, plant and equipment	(75,998)	(51,841)
Payments on landfill operating lease contracts	0	(5,006)
Proceeds from sale of property and equipment	542	609
Proceeds from property insurance settlement	332	992
Net cash used in investing activities	(148,620)	(109,916)
Cash Flows from Financing Activities:
Proceeds from long-term borrowings	121,500	566,800
Principal payments on long-term debt	(149,774)	(540,611)
Payments of debt issuance costs	0	(5,573)
Proceeds from the exercise of share based awards	3,355	471
Proceeds from the public issuance of Class A Common Stock	100,446	0
Proceeds from unregistered sale of Class A Common Stock	2,619	0
Net cash provided by financing activities	78,146	21,087
Net increase in cash and cash equivalents	1,021	1,088
Cash and cash equivalents, beginning of period	4,007	1,995
Cash and cash equivalents, end of period	5,028	3,083
Cash paid during the period for:
Interest	17,200	16,950
Income taxes, net of refunds	84	84
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Non-current assets obtained through long-term obligations	9,797	4,342
Contingent consideration from business combinations	0	2,924
Landfill
Adjustments to reconcile net income to net cash provided by operating activities:
Operating lease right-of-use assets expense	5,580
Cash Flows from Investing Activities:
Proceeds from property insurance settlement	$ 0	$ 3,506

BASIS OF PRESENTATION	9 Months Ended
BASIS OF PRESENTATION	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION Casella Waste Systems, Inc. (“Parent”), and its consolidated subsidiaries (collectively, “we”, “us” or “our”), is a regional, vertically integrated solid waste services company that provides collection, transfer, disposal, landfill, landfill gas-to-energy, recycling and organics services in the northeastern United States. We market recyclable metals, aluminum, plastics, paper, and corrugated cardboard, which have been processed at our recycling facilities, as well as recyclables purchased from third-parties. We manage our solid waste operations on a geographic basis through two regional operating segments, the Eastern and Western regions, each of which provides a full range of solid waste services, and our larger-scale recycling and commodity brokerage operations through our Recycling segment. Organics services, ancillary operations, along with major account and industrial services are included in our Other segment. The accompanying unaudited consolidated financial statements, which include the accounts of the Parent and our wholly-owned subsidiaries, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). All significant intercompany accounts and transactions are eliminated in consolidation. Investments in entities in which we do not have a controlling financial interest are accounted for under either the equity method or the cost method of accounting, as appropriate. Our significant accounting policies are more fully discussed in Item 8 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2018, which was filed with the SEC on February 22, 2019. Preparation of our consolidated financial statements in accordance with GAAP requires management to make certain estimates and assumptions. These estimates and assumptions affect the accounting for and recognition and disclosure of assets, liabilities, equity, revenues and expenses. We must make these estimates and assumptions because certain information that we use is dependent on future events, cannot be calculated with a high degree of precision given the available data, or simply cannot be readily calculated. In the opinion of management, these consolidated financial statements include all adjustments, which include normal recurring and nonrecurring adjustments, necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented. The results for the three and nine months ended September 30, 2019 may not be indicative of the results for any other interim period or the entire fiscal year. The consolidated financial statements presented herein should be read in conjunction with our audited consolidated financial statements included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2018. Subsequent Events We have evaluated subsequent events or transactions that have occurred after the consolidated balance sheet date of September 30, 2019 through the date of filing of the consolidated financial statements with the SEC on this Quarterly Report on Form 10-Q. We have determined that, except as disclosed, there are no subsequent events that require disclosure in this Quarterly Report on Form 10-Q.

ACCOUNTING CHANGES

9 Months Ended

Sep. 30, 2019

Accounting Changes and Error Corrections [Abstract]

ACCOUNTING CHANGES

A table providing a brief description of recent Accounting Standards Updates ("ASUs") to the Accounting Standards Codification (“ASC”) issued by the Financial Accounting Standards Board (“FASB”) that we adopted and deemed to have a material impact on our consolidated financial statements based on current account balances and activity follows:

Standard

Description

Effect on the Financial Statements or Other
Significant Matters

Accounting standards adopted effective January 1, 2019

ASU No. 2016-02, as amended through March 2019: Leases (Topic 842)

Requires that a lessee recognize at the commencement date: a lease liability, which is the obligation of the lessee to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term.

We adopted the guidance using the prospective optional transition method effective January 1, 2019, which allowed us to elect not to restate comparative periods and, if applicable, to recognize the effects of applying this guidance as a cumulative-effect adjustment to retained earnings as of January 1, 2019. We did not recognize a cumulative effect adjustment to retained earnings upon implementation. Upon adopting this guidance, we recognized a right-of-use asset and lease liability for leases classified as operating leases with a term in excess of 12 months in our consolidated balance sheet. We also prospectively reclassified landfill operating lease payments, along with related accumulated depreciation, that were previously capitalized as property, plant and equipment to operating lease right-of-use assets. Accordingly, the related cash outlays, which were historically considered cash flows from investing activities, were prospectively reclassified as cash flows from operating activities in accordance with Topic 842. With the assistance of third-party resources, we designed internal controls over the adoption of this guidance and implemented a third-party enterprise lease management software solution. In conjunction with the implementation, we modified our lease policy and internal business processes to effectively manage and account for leases, and to support recognition and disclosure requirements under the new standard. The adoption of this guidance did not have a material impact on the accounting for our finance leases. This guidance required additional disclosure over leases in order to comply with the new lease standard. See Note 5, Leases for additional disclosure.

A table providing a brief description of recent ASUs to the ASC issued by the FASB that are pending adoption and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity follows:

Standard

Description

Effect on the Financial Statements or Other
Significant Matters

Accounting standards issued pending adoption

ASU No. 2017-04: Intangibles - Goodwill and Other (Topic 350)

Requires that when an entity is performing its annual, or interim, goodwill impairment test, it should compare the fair value of the reporting unit with its carrying amount when calculating its impairment charge, noting that the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, if applicable, an entity should consider income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when calculating its impairment charge.

As of December 31, 2018, we did not record a goodwill impairment charge related to our annual goodwill impairment test because at that time the fair value of each reporting unit exceeded its respective carrying value. Upon adoption, if the carrying value of any of these reporting units exceeds the fair value when we perform a goodwill impairment test, we would record an impairment charge equal to the amount by which the carrying value exceeds its fair value. This guidance is effective January 1, 2020 with early adoption permitted for interim or annual goodwill impairment tests performed after January 1, 2017.

REVENUE RECOGNITION

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

A table of revenues disaggregated by service line and timing of revenue recognition by operating segment for each of the three and nine months ended September 30, 2019 and 2018 follows:

Three Months Ended September 30, 2019


	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	41,868	$	59,323	$	—	$	—	$	101,191
Landfill	5,414		20,018		—		—		25,432
Transfer	12,247		9,694		—		—		21,941
Customer solutions	—		—		—		20,689		20,689


Recycling	4		461		10,726		—		11,191


Organics	—		—		—		14,166		14,166
Transportation	—		2,709		—		420		3,129


Landfill gas-to-energy	142		666		—		—		808
Total revenues	$	59,675	$	92,871	$	10,726	$	35,275	$	198,547

Transferred at a point-in-time	$	36	$	186	$	4,592	$	1,156	$	5,970
Transferred over time	59,639		92,685		6,134		34,119		192,577
Total revenues	$	59,675	$	92,871	$	10,726	$	35,275	$	198,547

Three Months Ended September 30, 2018


	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	36,392	$	44,452	$	—	$	—	$	80,844
Landfill	8,336		18,764		—		—		27,100
Transfer	11,001		7,290		—		—		18,291
Customer solutions	—		—		—		17,195		17,195


Recycling	5		875		10,877		—		11,757


Organics	—		—		—		13,413		13,413
Transportation	—		2,396		—		916		3,312


Landfill gas-to-energy	272		648		—		—		920
Total revenues	$	56,006	$	74,425	$	10,877	$	31,524	$	172,832

Transferred at a point-in-time	$	128	$	233	$	7,436	$	1,138	$	8,935
Transferred over time	55,878		74,192		3,441		30,386		163,897
Total revenues	$	56,006	$	74,425	$	10,877	$	31,524	$	172,832

Nine Months Ended September 30, 2019



	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	115,363	$	163,070	$	—	$	—	$	278,433
Landfill	14,558		54,341		—		—		68,899
Transfer	33,157		23,566		—		—		56,723
Customer solutions	—		—		—		58,058		58,058


Recycling	5		1,243		32,006		—		33,254


Organics	—		—		—		42,668		42,668
Transportation	—		7,650		—		1,330		8,980


Landfill gas-to-energy	665		1,990		—		—		2,655
Total revenues	$	163,748	$	251,860	$	32,006	$	102,056	$	549,670

Transferred at a point-in-time	$	123	$	673	$	15,768	$	2,877	$	19,441
Transferred over time	163,625		251,187		16,238		99,179		530,229
Total revenues	$	163,748	$	251,860	$	32,006	$	102,056	$	549,670

Nine Months Ended September 30, 2018


	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	101,544	$	121,804	$	—	$	—	$	223,348
Landfill	22,179		49,504		—		—		71,683
Transfer	29,305		20,907		—		—		50,212
Customer solutions	—		—		—		48,315		48,315


Recycling	—		3,271		30,634		—		33,905


Organics	—		—		—		40,259		40,259
Transportation	—		11,779		—		2,421		14,200


Landfill gas-to-energy	1,071		2,943		—		—		4,014
Total revenues	$	154,099	$	210,208	$	30,634	$	90,995	$	485,936

Transferred at a point-in-time	$	500	$	847	$	20,311	$	3,219	$	24,877
Transferred over time	153,599		209,361		10,323		87,776		461,059
Total revenues	$	154,099	$	210,208	$	30,634	$	90,995	$	485,936

Contract receivables, which are included in Accounts receivable, net are recorded when billed or when related revenue is earned, if earlier, and represent claims against third-parties that will be settled in cash. Accounts receivable, net includes gross receivables from contracts of $90,291 and $73,500 as of September 30, 2019 and December 31, 2018, respectively. Certain customers are billed in advance and, accordingly, recognition of the related revenues is deferred as a contract liability until the services are provided and control transferred to the customer. We recognized contract liabilities of $2,812 and $3,074 as of September 30, 2019 and December 31, 2018, respectively. Due to the short term nature of advanced billings, substantially all of the deferred revenue recognized as a contract liability as of December 31, 2018 and December 31, 2017 were recognized as revenue during the three and nine months ended September 30, 2019 and September 30, 2018, respectively, when the services were performed.

BUSINESS COMBINATIONS

9 Months Ended

Sep. 30, 2019

Business Combinations [Abstract]

BUSINESS COMBINATIONS

BUSINESS COMBINATIONSIn the nine months ended September 30, 2019, we acquired eight businesses: three tuck-in solid waste collection businesses in our Eastern region and three tuck-in solid waste collection businesses, a business comprised of solid waste collection, transfer and recycling operations, and a business comprised of solid waste hauling and transfer assets in our Western region. In the nine months ended September 30, 2018, we acquired one solid waste collection, transfer and processing business in our Eastern region and three solid waste collection businesses, including a transfer station, in our Western region. The operating results of these businesses are included in the accompanying unaudited consolidated statements of operations from each date of acquisition, and the purchase price has been allocated to the net assets acquired based on fair values at each date of acquisition, with the residual amounts recorded as goodwill. Acquired intangible assets other than goodwill that are subject to amortization include client lists and non-compete covenants. Such assets are amortized over a five to ten year period from the date of acquisition. All amounts recorded to goodwill, except amounts related to certain acquisitions, are expected to be deductible for tax purposes.

A summary of the purchase price paid for these acquisitions and the allocation of the purchase price for these acquisitions follows:


	Nine Months Ended September 30,
	2019		2018
Purchase Price:
Cash used in acquisitions, net of cash acquired	$	71,038	$	57,824
Notes payable	2,714		—
Common stock	—		4,258
Other non-cash consideration	5,470		—
Contingent consideration and holdbacks	1,755		4,996
Total	80,977		67,078
Allocated as follows:
Current assets	1,935		2,968
Other non-current assets	367		—
Land	2,487		—
Buildings	5,422		7,539
Equipment	20,592		11,520
Intangible assets	31,171		20,300
Other liabilities, net	(3,040)		(2,443)
Deferred tax liability	(2,137)		(1,230)
Fair value of assets acquired and liabilities assumed	56,797		38,654
Excess purchase price allocated to goodwill	$	24,180	$	28,424

Certain purchase price allocations are preliminary and are based on information existing at the acquisition dates or upon closing the transaction. Accordingly, these purchase price allocations are subject to change. Unaudited pro forma combined information that shows our operational results as though each acquisition completed since the beginning of the prior fiscal year had occurred as of January 1, 2018 is as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Revenues	$	204,293	$	196,686	$	579,390	$	561,912
Operating income	$	19,369	$	31,505	$	42,321	$	53,051
Net income	$	12,905	$	23,794	$	24,810	$	24,745

Basic earnings per share attributable to common stockholders:
Weighted average common shares outstanding	47,690		42,779		47,029		42,605
Basic earnings per common share	$	0.27	$	0.56	$	0.53	$	0.58
Diluted earnings per share attributable to common stockholders:
Weighted average shares outstanding	48,361		44,175		47,660		43,938
Diluted earnings per common share	$	0.27	$	0.54	$	0.52	$	0.56

The unaudited pro forma results set forth in the table above have been prepared for comparative purposes only and are not necessarily indicative of the actual results of operations had the acquisitions occurred as of January 1, 2018 or of the results of our future operations. Furthermore, the unaudited pro forma results do not give effect to all cost savings or incremental costs that may occur as a result of the integration and consolidation of the completed acquisitions.

LEASES

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

LEASES

We lease vehicles, equipment, property and other non-core equipment in the ordinary course of our business. Leases are classified as either operating leases or finance leases, as appropriate. Our leases have varying terms and may include renewal or purchase options, escalation clauses, restrictions, lease concessions, capital project funding, penalties or other obligations that we considered historically in determining minimum rental payments. We recognize lease expense for operating leases on a straight-line basis over the lease term. We recognize depreciation expense for finance leases over either the useful life of the asset or the lease term based on the terms of the lease agreement.

We are also party to landfill operation and management agreements. These agreements are long-term landfill operating contracts with government bodies whereby we receive tipping revenue, pay normal operating expenses and assume future final capping, closure and post-closure obligations. The government body retains ownership of the landfill. There is no bargain purchase option and title to the property does not pass to us at the end of the lease term. We allocate the consideration paid to the landfill airspace rights and underlying land lease based on the relative fair values. In addition to up-front or one-time payments, the landfill operating agreements may require us to make future minimum rental payments, including success/expansion fees, other direct costs and final capping, closure and post-closure costs. The value of all future minimum rental payments is amortized and charged to cost of operations over the life of the contract on a units-of-consumption basis as airspace is utilized (e.g., as tons are placed into the landfill). The underlying value of any land lease is amortized to cost of operations on a straight-line basis over the estimated life of the operating agreement.

As a part of the implementation of Topic 842, we elected to adopt the practical expedient package and to not elect the hindsight practical expedient in determining lease term. The practical expedient package allowed us to: 1) not reassess lease classification for existing leases; 2) not reassess whether a contract contains a lease for existing contracts; and 3) not reassess initial direct costs for existing leases. Accordingly, we retained the operating lease and finance lease classifications in all periods presented and did not alter Topic 840 accounting over operating leases in place at transition allowing us to use historical minimum rental payments when determining the right-of-use asset and lease liability for existing operating leases. Upon adopting this guidance, we recognized a right-of-use asset and a lease liability for core leases classified as operating leases with a term in excess of 12 months in our consolidated balance sheet. For other non-core operating leases, which is comprised of small-dollar-value items such as office equipment, we continued to expense these costs in the period incurred rather than capitalizing such expenditures on our consolidated balance sheet. Accounting for finance leases was not impacted by the adoption of this guidance.

Under Topic 842, we identify lease and nonlease components in a contract to which consideration in the contract will be allocated. As an election, we may elect by class of underlying asset to choose not to separate nonlease components from lease components and instead account for each separate lease component and the nonlease components in a contract as part of the single lease component. We have elected to not separate lease components from nonlease components for property leases and are, therefore, not allocating consideration between lease and nonlease components for this asset class. Lease payments include: fixed payments, including in-substance fixed payments, less any lease incentives paid or payable to the lessee; variable lease payments that depend on an index or a rate; exercise price of a purchase option reasonably certain to be exercised; penalties for terminating a lease; and amounts where it is probable that we will owe under a residual value guarantee. Refundable deposits are not considered to be a fixed payment. Variable lease costs that are not based on an index or a rate are recorded to expense in the period incurred. Lease term is determined at lease commencement, and includes any noncancellable period for which we have the right to use the underlying asset together with any periods covered by an option to extend or terminate the lease if we are reasonably certain to exercise the option to extend or not to exercise the option to terminate. The initial determination of a lease liability is calculated as the net present value of the lease payments not yet paid. The discount rate used to determine present value is the rate implicit in the lease, if present, or, if not present, our incremental borrowing rate, which is a rate that reflects interest that we would have to pay to borrow funds on a collateralized basis over a similar term to the lease and in a similar economic environment. For shorter term leases, such as vehicle and equipment leases, we calculate our incremental borrowing rate using the interest rate from our existing secured line of credit, adjusted based on term. For longer term leases, such as our landfill operating leases, we calculate our incremental borrowing rate based on an industry yield curve with a similar credit rating, adjusted by a company specific spread as determined by a third-party.

A schedule of lease costs and other lease information follows:


	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Lease cost:
Amortization of right-of-use assets	$	593	$	1,505
Interest expense	213		555
Fixed lease cost - vehicles, equipment and property	2,351		7,271
Fixed lease cost - landfill operating leases	1,957		5,580
Fixed lease cost	4,308		12,851
Short-term lease cost	853		2,261
Variable lease cost	329		712
Total lease cost	$	6,296	$	17,884

Other information:
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows for finance leases	$	666	$	1,870
Operating cash flows for operating leases	$	2,963	$	9,837
Right-of-use assets obtained in exchange for new finance lease liabilities	$	—	$	6,857
Right-of-use assets obtained in exchange for new operating lease liabilities	$	831	$	1,419

			September 30, 2019
Weighted-average remaining lease term - finance leases (years)			6.7
Weighted-average remaining lease term - operating leases (years)			12.0
Weighted-average discount rate - finance leases			5.2		%
Weighted-average discount rate - operating leases			5.2		%

Estimated minimum future lease obligations are as follows:


	Operating Leases		Finance Leases
Fiscal year ending December 31, 2019	$	3,792	$	799
Fiscal year ending December 31, 2020	13,218		3,872
Fiscal year ending December 31, 2021	10,870		3,336
Fiscal year ending December 31, 2022	8,494		2,740
Fiscal year ending December 31, 2023	6,652		2,572
Thereafter	69,323		6,924
Total lease payments	112,349		20,243
Less: interest expense	(30,857)		(3,733)
Lease liability balance	$	81,492	$	16,510

LEASES

A schedule of lease costs and other lease information follows:


	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Lease cost:
Amortization of right-of-use assets	$	593	$	1,505
Interest expense	213		555
Fixed lease cost - vehicles, equipment and property	2,351		7,271
Fixed lease cost - landfill operating leases	1,957		5,580
Fixed lease cost	4,308		12,851
Short-term lease cost	853		2,261
Variable lease cost	329		712
Total lease cost	$	6,296	$	17,884

Other information:
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows for finance leases	$	666	$	1,870
Operating cash flows for operating leases	$	2,963	$	9,837
Right-of-use assets obtained in exchange for new finance lease liabilities	$	—	$	6,857
Right-of-use assets obtained in exchange for new operating lease liabilities	$	831	$	1,419

			September 30, 2019
Weighted-average remaining lease term - finance leases (years)			6.7
Weighted-average remaining lease term - operating leases (years)			12.0
Weighted-average discount rate - finance leases			5.2		%
Weighted-average discount rate - operating leases			5.2		%

Estimated minimum future lease obligations are as follows:


	Operating Leases		Finance Leases
Fiscal year ending December 31, 2019	$	3,792	$	799
Fiscal year ending December 31, 2020	13,218		3,872
Fiscal year ending December 31, 2021	10,870		3,336
Fiscal year ending December 31, 2022	8,494		2,740
Fiscal year ending December 31, 2023	6,652		2,572
Thereafter	69,323		6,924
Total lease payments	112,349		20,243
Less: interest expense	(30,857)		(3,733)
Lease liability balance	$	81,492	$	16,510

GOODWILL AND INTANGIBLE ASSETS

9 Months Ended

Sep. 30, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND INTANGIBLE ASSETS

A summary of the activity and balances related to goodwill by reporting segment is as follows:


	December 31, 2018		Acquisitions		Other (1)		September 30, 2019
Eastern region	$	28,154	$	2,566	$	—	$	30,720
Western region	120,536		21,614		(2,619)		139,531
Recycling	12,315		—		—		12,315
Other	1,729		—		—		1,729
Total	$	162,734	$	24,180	$	(2,619)	$	184,295

(1)Relates to the unregistered sale of Class A common stock that was previously held in escrow and released to us for liquidation . See Note 10, Stockholders' Equity for additional disclosure.

A summary of intangible assets by intangible asset type follows:


	Covenants Not-to-Compete		Client Lists		Total
Balance, September 30, 2019
Intangible assets	$	26,162	$	71,122	$	97,284
Less accumulated amortization	(18,575)		(17,726)		(36,301)
	$	7,587	$	53,396	$	60,983


	Covenants Not-to-Compete		Client Lists		Total
Balance, December 31, 2018
Intangible assets	$	21,750	$	44,363	$	66,113
Less accumulated amortization	(17,584)		(13,762)		(31,346)
	$	4,166	$	30,601	$	34,767

Intangible amortization expense was 1,916 and 4,956 during the three and nine months ended September 30, 2019, respectively, as compared to $714 and $1,848 during the three and nine months ended September 30, 2018, respectively.

A summary of intangible amortization expense estimated for the five fiscal years following the fiscal year ended December 31, 2018 and thereafter follows:



Estimated Future Amortization Expense as of September 30, 2019
Fiscal year ending December 31, 2019	$	2,264
Fiscal year ending December 31, 2020	$	8,222
Fiscal year ending December 31, 2021	$	6,826
Fiscal year ending December 31, 2022	$	6,188
Fiscal year ending December 31, 2023	$	5,993
Thereafter	$	31,490

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE

9 Months Ended

Sep. 30, 2019

Asset Retirement Obligation Disclosure [Abstract]

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE

Accrued final capping, closure and post-closure costs include the current and non-current portion of costs associated with obligations for final capping, closure and post-closure of our landfills. We estimate our future final capping, closure and post-closure costs in order to determine the final capping, closure and post-closure expense per ton of waste placed into each landfill. The anticipated time frame for paying these costs varies based on the remaining useful life of each landfill as well as the duration of the post-closure monitoring period.

A summary of the changes to accrued final capping, closure and post-closure liabilities follows:


	Nine Months Ended September 30,
	2019		2018
Beginning balance	$	73,075	$	62,290
Obligations incurred	1,901		2,874
Revision in estimates (1)	—		1,492
Accretion expense	4,742		4,175

Obligations settled (2)	(7,099)		(2,310)
Ending balance	$	72,619	$	68,521

(1)Relates to changes in estimates and assumptions associated with anticipated costs of future final capping, closure and post-closure activities at the Town of Southbridge, Massachusetts landfill. See Note 9, Commitments and Contingencies and Note 12, Other Items and Charges for additional disclosure regarding the matter.

(2)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.

LONG-TERM DEBT

9 Months Ended

Sep. 30, 2019

Debt And Derivatives Disclosure [Abstract]

LONG-TERM DEBT

A summary of long-term debt and finance leases by debt instrument follows:


	September 30, 2019		December 31, 2018
Senior Secured Credit Facility:
Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.75%	$	43,400	$	69,600
Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.75%	350,000		350,000

Tax-Exempt Bonds:
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014 ("New York Bonds 2014") due December 2044 - fixed rate interest period through 2019; bearing interest at 3.75%	25,000		25,000
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 ("New York Bonds 2014R-2") due December 2044 - fixed rate interest period through 2026; bearing interest at 3.125%	15,000		15,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 ("FAME Bonds 2005R-3") due January 2025 - fixed rate interest period through 2025; bearing interest at 5.25%	25,000		25,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-1 ("FAME Bonds 2015R-1") due August 2035 - fixed rate interest period through 2025; bearing interest at 5.125%	15,000		15,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2 ("FAME Bonds 2015R-2") due August 2035 - fixed rate interest period through 2025; bearing interest at 4.375%	15,000		15,000
Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 ("Vermont Bonds") due April 2036 - fixed rate interest period through 2028; bearing interest at 4.625%	16,000		16,000
Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 ("New Hampshire Bonds") due April 2029 - fixed rate interest period through September 2019; bore interest at 4.00%	11,000		11,000
Other:
Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2%	16,510		11,248
Notes payable maturing through June 2027; bearing interest at a weighted average of 3.5%	4,862		2,401
Principal amount of long-term debt and finance leases	536,772		555,249
Less—unamortized debt issuance costs (1)	9,226		10,950
Long-term debt and finance leases less unamortized debt issuance costs	527,546		544,299
Less—current maturities of long-term debt and finance leases	3,571		2,298
	$	523,975	$	542,001

(1)A summary of unamortized debt issuance costs by debt instrument follows:


	September 30, 2019		December 31, 2018
Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility")	$	5,889	$	7,118
New York Bonds 2014	707		847
New York Bonds 2014R-2	405		450
FAME Bonds 2005R-3	453		517
FAME Bonds 2015R-1	569		622
FAME Bonds 2015R-2	436		493
Vermont Bonds	554		595
New Hampshire Bonds	213		308
	$	9,226	$	10,950

Financing Activities

In October 2019, we completed the remarketing of $11,000 aggregate principal amount of New Hampshire Bonds. The New Hampshire Bonds, which are unsecured and guaranteed jointly and severally, fully and unconditionally by all of our significant wholly-owned subsidiaries, accrue interest at 2.95% per annum from October 1, 2019 through final maturity on April 1, 2029.

Credit Facility

As of September 30, 2019, we are party to a credit agreement ("Credit Agreement"), which provides for a $350,000 Term Loan Facility and a $200,000 Revolving Credit Facility. We have the right to request, at our discretion, an increase in the amount of loans under the Credit Facility by an aggregate amount of $125,000, subject to the terms and conditions set forth in the Credit Agreement.

The Credit Facility has a 5-year term that matures in May 2023 and bears interest at a rate of LIBOR plus 1.75% per annum, which will be reduced to a rate of LIBOR plus, as low as, 1.25% upon us reaching a consolidated net leverage ratio of less than 2.25x. The Credit Facility is guaranteed jointly and severally, fully and unconditionally by all of our significant wholly-owned subsidiaries and secured by substantially all of our assets. As of September 30, 2019, further advances were available under the Credit Facility in the amount of $131,979. The available amount is net of outstanding irrevocable letters of credit totaling $24,621, at which date no amount had been drawn.

The Credit Agreement requires us to maintain a minimum interest coverage ratio and a maximum consolidated net leverage ratio, to be measured at the end of each fiscal quarter. As of September 30, 2019, we were in compliance with the covenants contained in the Credit Agreement. In addition to these financial covenants, the Credit Agreement also contains a number of important customary affirmative and negative covenants which restrict, among other things, our ability to sell assets, incur additional debt, create liens, make investments, and pay dividends. We do not believe that these restrictions impact our ability to meet future liquidity needs. An event of default under any of our debt agreements could permit some of our lenders, including the lenders under the Credit Facility, to declare all amounts borrowed from them to be immediately due and payable, together with accrued and unpaid interest, or, in the case of the Credit Facility, terminate the commitment to make further credit extensions thereunder, which could, in turn, trigger cross-defaults under other debt obligations. If we were unable to repay debt to our lenders, or were otherwise in default under any provision governing our outstanding debt obligations, our secured lenders could proceed against us and against the collateral securing that debt.

Loss on Debt Extinguishment

We recorded a loss on debt extinguishment of $7,352 in the nine months ended September 30, 2018 associated with the write-off of debt issuance costs and unamortized discount in connection with the refinancing of our term loan B facility with our existing Credit Facility, and the write-off of debt issuance costs in connection with the remarketing of our Vermont Bonds.

Cash Flow Hedges

As of September 30, 2019, we had in place nine interest rate derivative agreements to hedge interest rate risk associated with the variable rate portion of our long-term debt. The hedging relationships between these interest rate derivative agreements and the variable rate interest payments related to the Term Loan Facility were originally considered highly effective based on quantitative assessments using regression analysis and, subsequently, based on a qualitative assessment performed as of September 30, 2019. Therefore, we have designated these derivative instruments as effective cash flow hedges.

The total notional amount of all of our interest rate derivative agreements is $190,000 and according to the terms of the agreements, we receive interest based on the 1-month LIBOR index and pay interest at a weighted average rate of approximately 2.54%. The agreements mature between February 2021 and May 2023.

A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows:


		Fair Value
	Balance Sheet Location	September 30, 2019		December 31, 2018
Interest rate swaps	Other current assets	$	—	$	338
Interest rate swaps	Other non-current assets	—		482
		$	—	$	820

Interest rate swaps	Other accrued liabilities	$	1,686	$	387
Interest rate swaps	Other long-term liabilities	4,398		1,555
		$	6,084	$	1,942

Interest rate swaps	Accumulated other comprehensive loss	$	(6,459)	$	(1,196)
Interest rate swaps - tax provision	Accumulated other comprehensive loss	(112)		(112)
		$	(6,571)	$	(1,308)

A summary of the amount of expense on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income (loss) into earnings follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Statement of Operations Location	(Expense) Income						(Expense) Income
Interest expense	$	(147)	$	(156)	$	(216)	$	(247)

COMMITMENTS AND CONTINGENCIES

9 Months Ended

Sep. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Legal Proceedings

In the ordinary course of our business and as a result of the extensive governmental regulation of the solid waste industry, we are subject to various judicial and administrative proceedings involving state and local agencies. In these proceedings, an agency may seek to impose fines or to revoke or deny renewal of an operating permit held by us. From time to time, we may also be subject to actions brought by special interest or other groups, adjacent landowners or residents in connection with the permitting and licensing of landfills and transfer stations, or allegations of environmental damage or violations of the permits and licenses pursuant to which we operate. In addition, we may be named defendants in various claims and suits pending for alleged damages to persons and property, alleged violations of certain laws and alleged liabilities arising out of matters occurring during the ordinary operation of a waste management business.

In accordance with FASB ASC 450 - Contingencies, we accrue for legal proceedings, inclusive of legal costs, when losses become probable and reasonably estimable. As of the end of each applicable reporting period, we review each of our legal proceedings to determine whether it is probable, reasonably possible or remote that a liability has been incurred and, if it is at least reasonably possible, whether a range of loss can be reasonably estimated under the provisions of FASB ASC 450-20. In instances where we determine that a loss is probable and we can reasonably estimate a range of loss we may incur with respect to such a matter, we record an accrual for the amount within the range that constitutes our best estimate of the possible loss. If we are able to reasonably estimate a range, but no amount within the range appears to be a better estimate than any other, we record an accrual in the amount that is the low end of such range. When a loss is reasonably possible, but not probable, we will not record an accrual, but we will disclose our estimate of the possible range of loss where such estimate can be made in accordance with FASB ASC 450-20.

Environmental Remediation Liability (including related litigation)

We are subject to liability for environmental damage, including personal injury and property damage, that our solid waste, recycling and power generation facilities may cause to neighboring property owners, particularly as a result of the contamination of drinking water sources or soil, possibly including damage resulting from conditions that existed before we acquired the facilities. We may also be subject to liability for similar claims arising from off-site environmental contamination caused by pollutants or hazardous substances if we or our predecessors arrange or arranged to transport, treat or dispose of those materials. The following matters represent our material outstanding claims.

Southbridge Recycling & Disposal Park, Inc.

In October 2015, our Southbridge Recycling and Disposal Park, Inc. (“SRD”) subsidiary reported to the Massachusetts Department of Environmental Protection (“MADEP”) results of analysis of samples collected pursuant to our existing permit from private drinking water wells located near the Town of Southbridge, Massachusetts (“Town”) Landfill (“Southbridge Landfill”), which was operated by SRD and later closed in November 2018 when Southbridge Landfill reached its final capacity. Those results indicated the presence of contaminants above the levels triggering notice and response obligations under MADEP regulations. In response to those results, we are carrying out an Immediate Response Action pursuant to Massachusetts General Law Chapter 21E (the "Charlton 21E Obligations") pursuant to state law. Further, we have implemented a plan to analyze and better understand the groundwater near the Southbridge Landfill and we are investigating with the objective of identifying the source or sources of the elevated levels of contamination measured in the well samples. If it is determined that some or all of the contamination originated at the Southbridge Landfill, we will work with the Town (the Southbridge Landfill owner and the former operator of an unlined portion of the Southbridge Landfill, which was used prior to our operation of a double-lined portion of the Southbridge Landfill commencing in 2004) to evaluate and allocate the liabilities related to the Charlton 21E Obligations. In July 2016, we sent correspondence to the Town pursuant to Chapter 21E of Massachusetts General Laws demanding that the Town reimburse us for the environmental response costs we had spent and that the Town be responsible for all such costs in the future, as well as any other costs or liabilities resulting from the release of contaminants from the unlined portion of the Southbridge Landfill. The Town responded in September 2016, denying that the Southbridge Landfill is the source of such contamination, and claiming that if it is, that we may owe an indemnity to the Town pursuant to the Operating Agreement between us and the Town dated May 29, 2007, as amended. We entered into a Tolling Agreement with the Town to delay any further administrative or legal actions until our work with MADEP more specifically defines the parties’ responsibilities for the Charlton 21E Obligations, if any. Please see below for further discussion of our relationship with the Town regarding the Charlton 21E Obligations.

In February 2016, we and the Town received a Notice of Intent to Sue under the Resource Conservation and Recovery Act ("RCRA") from a law firm purporting to represent residents proximate to the Southbridge Landfill (“Residents”), indicating its intent to file suit against us on behalf of the Residents alleging the groundwater contamination originated from the Southbridge Landfill. In February 2017, we received an additional Notice of Intent to Sue from the National Environmental Law Center under the Federal Clean Water Act ("CWA") and RCRA (collectively the “Acts”) on behalf of Environment America, Inc., d/b/a Environment Massachusetts, and Toxics Action Center, Inc., which have referred to themselves as the Citizen Groups. The Citizen Groups alleged that we had violated the Acts, and that they intended to seek appropriate relief in federal court for those alleged violations. On or about June 9, 2017, a lawsuit was filed against us, SRD and the Town in the United States District Court for the District of Massachusetts (the “Massachusetts Court”) by the Citizen Groups and the Residents alleging violations of the Acts (the “Litigation”), and demanding a variety of remedies under the Acts, including fines, remediation, mitigation and costs of litigation, and remedies for violations of Massachusetts civil law related to personal and property damages, including remediation, diminution of property values, compensation for lost use and enjoyment of properties, enjoinment of further operation of the Southbridge Landfill, and costs of litigation, plus interest on any damage award, on behalf of the Residents. We believe the Litigation to be factually inaccurate, and without legal merit, and we and SRD intend to vigorously defend the Litigation. Nevertheless, we believe it is reasonably possible that a loss will occur as a result of the Litigation although an estimate of loss cannot be reasonably provided at this time. We also continue to believe the Town should be responsible for costs or liabilities associated with the Litigation relative to alleged contamination originating from the unlined portion of the Southbridge Landfill, although there can be no assurance that we will not be required to incur some or all of such costs and liabilities.

In December 2017, we filed a Motion to Dismiss the Litigation, and on October 1, 2018, the Massachusetts Court granted our Motion to Dismiss, and accordingly, dismissed the Citizen Groups claims under the Acts. The Massachusetts Court has retained jurisdiction of the Residents claims. The Citizen Groups intend to appeal the Massachusetts Court’s decision to grant our Motion to Dismiss. The Residents moved for a stay of their case until the Citizen Groups appealed. We opposed the stay and in March 2019, the Massachusetts Court denied the Residents motion for a stay.

We entered into an Administrative Consent Order on April 26, 2017 (the “ACO”), with MADEP, the Town, and the Town of Charlton, committing us to equally share the costs with MADEP, of up to $10,000 ($5,000 each) for the Town to install a municipal waterline in the Town of Charlton ("Waterline"). Upon satisfactory completion of that Waterline, and other matters covered by the ACO, we and the Town will be released by MADEP from any future responsibilities for the Charlton 21E Obligations. We also entered into an agreement with the Town on April 28, 2017 entitled the “21E Settlement and Water System Construction Funding Agreement” (the “Waterline Agreement”), wherein we and the Town released each other from claims arising from the Charlton 21E Obligations. Pursuant to the Waterline Agreement, the Town will issue a twenty (20) year bond for our portion of the Waterline costs (up to $5,000). We have agreed to reimburse the Town for periodic payments under such bond. Construction of the waterline is near completion and expected to be completed in the fiscal year ending December 31, 2019.

We have recorded an environmental remediation liability associated with the future installation of the Waterline in other accrued liabilities and other long-term liabilities. We inflate the estimated costs in current dollars to the expected time of payment and discount the total cost to present value using a risk-free interest rate of 2.6%. Our expenditures could be significantly higher if costs exceed estimates. The changes to the environmental remediation liability associated with the Southbridge Landfill are as follows:



	Nine Months Ended September 30,
	2019		2018
Beginning balance	$	5,173	$	5,936
Accretion expense	94		116


Obligations settled (1)	(556)		(612)
Ending balance	$	4,711	$	5,440

(1)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.

The costs and liabilities we may be required to incur in connection with the foregoing Southbridge Landfill matters could be material to our results of operations, our cash flows and our financial condition.

Potsdam Environmental Remediation Liability

On December 20, 2000, the State of New York Department of Environmental Conservation (“DEC”) issued an Order on Consent (“Order”) which named Waste-Stream, Inc. (“WSI”), our subsidiary, General Motors Corporation (“GM”) and Niagara Mohawk Power Corporation (“NiMo”) as Respondents. The Order required that the Respondents undertake certain work on a 25-acre scrap yard and solid waste transfer station owned by WSI in Potsdam, New York, including the preparation of a Remedial Investigation and Feasibility Study (“Study”). A draft of the Study was submitted to the DEC in January 2009 (followed by a final report in May 2009). The Study estimated that the undiscounted costs associated with implementing the preferred remedies would be approximately $10,219. On February 28, 2011, the DEC issued a Proposed Remedial Action Plan for the site and accepted public comments on the proposed remedy through March 29, 2011. We submitted comments to the DEC on this matter. In April 2011, the DEC issued the final Record of Decision (“ROD”) for the site. The ROD was subsequently rescinded by the DEC for failure to respond to all submitted comments. The preliminary ROD, however, estimated that the present cost associated with implementing the preferred remedies would be approximately $12,130. The DEC issued the final ROD in June 2011 with proposed remedies consistent with its earlier ROD. An Order on Consent and Administrative Settlement naming WSI and NiMo as Respondents was executed by the Respondents and DEC with an effective date of October 25, 2013. On January 29, 2016, a Cost-Sharing Agreement was executed between WSI, NiMo, Alcoa Inc. (“Alcoa”) and Reynolds Metal Company (“Reynolds”) whereby Alcoa and Reynolds elected to voluntarily participate in the onsite remediation activities at a combined 15% participant share. The remediation work has commenced and it is expected that the majority of the remediation work will be completed in the fiscal year ending December 31, 2019. WSI is jointly and severally liable with NiMo, Alcoa and Reynolds for the total cost to remediate.

We have recorded an environmental remediation liability associated with the Potsdam site based on incurred costs to date and estimated costs to complete the remediation in other accrued liabilities and other long-term liabilities. Our expenditures could be significantly higher if costs exceed estimates. We inflate the estimated costs in current dollars to the expected time of payment and discount the total cost to present value using a risk-free interest rate of 1.5%.

A summary of the changes to the environmental remediation liability associated with the Potsdam environmental remediation liability follows:



	Nine Months Ended September 30,
	2019		2018
Beginning balance	$	5,614	$	5,758



Obligations settled (1)	(1,764)		(98)
Ending balance	$	3,850	$	5,660

(1)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.

North Country Environmental Services

On or about March 8, 2018, the Citizen Groups described above delivered correspondence to our subsidiary, North Country Environmental Services, Inc. ("NCES") and us, providing notice of the Citizen Groups' intent to sue NCES and us for violations of the CWA in conjunction with NCES's operation of its landfill in Bethlehem, New Hampshire. On May 14, 2018, the Citizen Groups filed a lawsuit against NCES and us in the United States District Court for the District of New Hampshire (the “New Hampshire Court”) alleging violations of the CWA, arguing that ground water discharging into the Ammonoosuc River is a "point source" under the CWA (the "New Hampshire Litigation"). The New Hampshire Litigation seeks remediation and fines under the CWA. On June 15, 2018, we and NCES filed a Motion to Dismiss the New Hampshire Litigation. On July 13, 2018, the Citizen Groups filed objections to our Motion to Dismiss. On July 27, 2018, we filed a reply in support of our Motion to Dismiss. On September 25, 2018, the New Hampshire Court denied our Motion to Dismiss. In March of 2019, we filed a motion in the New Hampshire Litigation asking for a stay of this litigation until certain appeals from discordant federal circuits were heard by the Supreme Court of the United States (“SCOTUS”). SCOTUS has granted certiorari determining that the circumstances described are sufficient for SCOTUS to hear such cases. Our motion for a stay was granted in the New Hampshire Litigation, and SCOTUS is expected to hear and rule on such cases this calendar year. In any event, we intend to continue to vigorously defend against the New Hampshire Litigation, which we believe is without merit.

Ontario County, New York Class Action LitigationOn or about September 17, 2019, Richard Vandemortel and Deb Vandemortel filed a class action complaint against us on behalf of similarly situated citizens in Ontario County, New York. The lawsuit has been filed in Ontario County (the “New York Litigation”). It alleges that over one thousand (1,000) citizens constitute the putative class in the New York Litigation, and it seeks damages for diminution of property values and infringement of the putative class’ rights to live without interference to their daily lives due to odors emanating from the Ontario County Landfill, which is operated by us pursuant to a long-term Operation, Maintenance and Lease Agreement with Ontario County. The New York Litigation was served on us on October 14, 2019. We are reviewing the New York Litigation and intend to present a vigorous defense.

STOCKHOLDERS' EQUITY

9 Months Ended

Sep. 30, 2019

Equity [Abstract]

STOCKHOLDERS' EQUITY

Recent Developments

In the nine months ended September 30, 2019, we completed a public issuance of 3,565 shares of our Class A common stock at a public offering price of $29.50 per share. The offering resulted in net proceeds to us of $100,446, after deducting underwriting discounts and commissions and offering expenses. The net proceeds from the offering were and are to be used for general corporate purposes, including potential acquisitions or development of new operations or assets with the goal of complementing or expanding our business, working capital and capital expenditures.

In the three and nine months ended September 30, 2019, we completed the unregistered sale of 59 shares of our Class A common stock at a price of $44.15 per share. The sale resulted in net proceeds to us of $2,618. The shares were previously held in escrow according to the terms of our acquisition of WSI and released to us for liquidation to offset costs associated with the environmental remediation of the WSI's Potsdam, New York site. We recorded a $2,618 reduction of goodwill in line with business combination standards in place at the time the shares held in escrow were issued. See Note 9, Commitments and Contingencies for additional disclosure.

Stock Based Compensation

Shares Available For Issuance

In the fiscal year ended December 31, 2016, we adopted the 2016 Incentive Plan (“2016 Plan”). Under the 2016 Plan, we may grant awards up to an aggregate amount of shares equal to the sum of: (i) 2,250 shares of Class A common stock (subject to adjustment in the event of stock splits and other similar events), plus (ii) such additional number of shares of Class A common stock (up to 2,723 shares) as is equal to the sum of the number of shares of Class A common stock that remained available for grant under the 2006 Stock Incentive Plan (“2006 Plan”) immediately prior to the expiration of the 2006 Plan and the number of shares of Class A common stock subject to awards granted under the 2006 Plan that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by us. As of September 30, 2019, there were 1,399 Class A common stock equivalents available for future grant under the 2016 Plan.

Stock Options

Stock options are granted at a price equal to the prevailing fair value of our Class A common stock at the date of grant. Generally, stock options granted have a term not to exceed ten years and vest over a one year to four year period from the date of grant.

The fair value of each stock option granted is estimated using a Black-Scholes option-pricing model, which requires extensive use of accounting judgment and financial estimation, including estimates of the expected term stock option holders will retain their vested stock options before exercising them and the estimated volatility of our Class A common stock price over the expected term.

A summary of stock option activity follows:


	Stock Options (1)	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2018	669	$	6.37
Granted	—	$	—
Exercised	(571)	$	5.88
Forfeited	—	$	—
Outstanding, September 30, 2019	98	$	9.20	6.1	$	3,311
Exercisable, September 30, 2019	98	$	9.20	6.1	$	3,311

Stock-based compensation expense for stock options was $0 and $0 during the three and nine months ended September 30, 2019, respectively, as compared to $127 and $377 during the three and nine months ended September 30, 2018, respectively.

During the three and nine months ended September 30, 2019, the aggregate intrinsic value of stock options exercised was $7,741 and $19,475, respectively.

Other Stock Awards

Restricted stock awards, restricted stock units and performance stock units, with the exception of market-based performance stock units, are granted at a price equal to the fair value of our Class A common stock at the date of grant. The fair value of each market-based performance stock unit is estimated using a Monte Carlo pricing model, which requires extensive use of accounting judgment and financial estimation, including the estimated share price appreciation plus the value of dividends of our Class A common stock as compared to the Russell 2000 Index over the requisite service period.

Generally, restricted stock awards granted to non-employee directors vest incrementally over a three year period beginning on the first anniversary of the date of grant. Restricted stock units granted to non-employee directors typically vest in full on the first anniversary of the grant date. Restricted stock units granted to employees vest incrementally over an identified service period beginning on the grant date based on continued employment. Performance stock units granted to employees, including market-based performance stock units, vest at a future date following the grant date and are based on the attainment of performance targets and market achievements, as applicable.

A summary of restricted stock, restricted stock unit and performance stock unit activity follows:


	Restricted Stock, Restricted Stock Units, and Performance Stock Units (1)	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2018	686	$	15.56
Granted	163	$	37.14
Class A Common Stock Vested	(217)	$	12.19
Forfeited	(7)	$	20.48
Outstanding, September 30, 2019	625	$	22.36	1.1	$	12,866
Unvested, September 30, 2019	950	$	21.90	1.0	$	19,998

(1)Market-based performance stock unit grants are included at the 100% attainment level. Attainment of the maximum performance targets and market achievements would result in the issuance of an additional 325 shares of Class A common stock currently included in unvested.

Stock-based compensation expense related to restricted stock, restricted stock units and performance stock units was $1,858 and $5,084 during the three and nine months ended September 30, 2019, respectively, as compared to $2,007 and $5,883 during the three and nine months ended September 30, 2018, respectively.

During the three and nine months ended September 30, 2019, the total fair value of other stock awards vested was $43 and $7,764, respectively.

As of September 30, 2019, total unrecognized stock-based compensation expense related to outstanding restricted stock and restricted stock units was $3,852, which will be recognized over a weighted average period of 1.4 years. As of September 30, 2019, maximum unrecognized stock-based compensation expense related to outstanding performance stock units, assuming the attainment of maximum performance targets, was $6,009 to be recognized over a weighted average period of 0.9 years.

We also recorded $40 and $134 of stock-based compensation expense related to our Amended and Restated 1997 Employee Stock Purchase Plan during the three and nine months ended September 30, 2019, respectively, as compared to $34 and $106 during the three and nine months ended September 30, 2018, respectively.

Accumulated Other Comprehensive Loss

A summary of the changes in the balances of each component of accumulated other comprehensive loss, net of tax follows:



	Interest Rate Swaps
Balance, December 31, 2018	$	(1,308)

Other comprehensive loss before reclassifications	(5,479)
Amounts reclassified from accumulated other comprehensive loss	216
Income tax provision related to items of other comprehensive loss	—
Net current-period other comprehensive loss	(5,263)
Balance, September 30, 2019	$	(6,571)

A summary of reclassifications out of accumulated other comprehensive loss, net of tax follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Details About Accumulated Other Comprehensive Loss Components	Amounts Reclassified Out of Accumulated Other Comprehensive Loss									Affected Line Item in the Consolidated Statements of Operations
Interest rate swaps	$	147	$	156	$	216	$	247	Interest expense
	147		156		216		247		Income before income taxes
	—		—		—		—		Provision (benefit) for income taxes
	$	147	$	156	$	216	$	247	Net income

EARNINGS PER SHARE

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

EARNINGS PER SHARE

EARNINGS PER SHAREBasic earnings per share is computed by dividing the net income by the weighted average number of common shares outstanding during the period. Diluted earnings per share is calculated based on the combined weighted average number of common shares and potentially dilutive shares, which include the assumed exercise of employee stock options, unvested restricted stock awards, unvested restricted stock units and unvested performance stock units, including market-based performance units based on the expected achievement of performance targets. In computing diluted earnings per share, we utilize the treasury stock method.

A summary of the numerator and denominators used in the computation of earnings per share follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Numerator:
Net income	$	12,386	$	22,302	$	22,587	$	20,096
Denominators:
Number of shares outstanding, end of period:
Class A common stock	46,792		41,932		46,792		41,932
Class B common stock	988		988		988		988
Shares to be issued - acquisition	36		—		36		—
Unvested restricted stock	(9)		(32)		(9)		(32)
Effect of weighted average shares outstanding	(117)		(109)		(778)		(283)
Basic weighted average common shares outstanding	47,690		42,779		47,029		42,605
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards	671		1,396		631		1,333
Diluted weighted average common shares outstanding	48,361		44,175		47,660		43,938
Anti-dilutive potentially issuable shares	2		—		2		2

OTHER ITEMS AND CHARGES

9 Months Ended

Sep. 30, 2019

Unusual or Infrequent Items, or Both [Abstract]

OTHER ITEMS AND CHARGES

Multiemployer Pension Plan

We make contributions to a multiemployer defined benefit pension plan, the New England Teamsters and Trucking Industry Pension Fund (the “Pension Plan”), under the terms of a collective bargaining agreement (“CBA”) that covers certain of our union represented employees. The Pension Plan provides retirement benefits to participants based on their service to contributing employers. We do not administer the Pension Plan. The risks of participating in a multiemployer pension plan are different from a single-employer pension plan in that: (i) assets contributed to the multiemployer pension plan by one employer may be used to provide benefits to employees or former employees of other participating employers; (ii) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be required to be assumed by the remaining participating employers; and (iii) if we choose to stop participating in our multiemployer Pension Plan, we may be required to pay the plan a withdrawal amount based on the underfunded status of the plan.

In October 2019, we reached an agreement to withdraw from the Pension Plan by entering into Withdrawal and Re-entry Agreements with the Pension Plan. In accordance with FASB ASC 450 - Contingencies, because of our withdrawal from the Pension Plan, we recorded an obligation of $3,194 as of September 30, 2019 and a charge of $3,591 as pension withdrawal expense, offset by a $397 retroactive contribution credit recorded as cost of operations, in the three and nine months ended September 30, 2019. While the withdrawal generates a fixed yearly contingent liability for us for a period of approximately seventeen (17) years, it caps our gross payments at $4,224 significantly reducing our cash exposure from the potential $18,511 withdrawal liability as determined based on a complete withdrawal. As per the Re-entry Agreements and upon withdrawal, we will re-enter the Pension Plan with certainty from a liability perspective. We have not, however, changed the terms of our CBA with Local 170, which remains in effect until June 30, 2020.

Expense from Acquisition Activities and Other Items

In the three and nine months ended September 30, 2019, we recorded charges of $1,097 and $2,237, respectively, associated primarily with acquisition activities. In the three and nine months ended September 30, 2018, we recorded charges of $0 and $211, respectively, associated with the write-off of deferred costs related to the expiration of our shelf registration statement and $581 and $719, respectively, associated with acquisition activities.

Southbridge Landfill Closure Charge (Settlement), Net

In June 2017, we initiated the plan to cease operations of the Southbridge Landfill and later closed it in November 2018 when Southbridge Landfill reached its final capacity. Accordingly, in the three and nine months ended September 30, 2019 and 2018, we recorded charges (settlement) associated with the closure of the Southbridge Landfill as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018



Charlton settlement charge (1)	$	—	$	—	$	—	$	1,216
Legal and other costs (2)	625		502		2,097		1,044
Recovery on insurance settlement (3)	—		(10,000)		—		(10,000)

Southbridge Landfill closure charge (settlement), net	$	625	$	(9,498)	$	2,097	$	(7,740)

(1)We established a reserve associated with settlement of the Town of Charlton's claim against us. See Note 9, Commitments and Contingencies for additional disclosure.

(2)We incurred legal costs as well as other costs associated with various matters as part of the Southbridge Landfill closure. See Note 9, Commitments and Contingencies for additional disclosure.

(3)We recorded a recovery on an environmental insurance settlement associated with the Southbridge Landfill closure. See Note 9, Commitments and Contingencies for additional disclosure.

Contract Settlement Charge

In the nine months ended September 30, 2018, we recorded a contract settlement charge of $2,100 associated with the termination and discounted buy-out of a commodities marketing and brokerage agreement.

Development Project Charge

In the nine months ended September 30, 2018, we recorded a development project charge of $311 associated with previously deferred costs that were written off as a result of the negative vote in a public referendum relating to the NCES landfill.

FAIR VALUE OF FINANCIAL INSTRUMENTS

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

FAIR VALUE OF FINANCIAL INSTRUMENTS

We use a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. These tiers include: Level 1, defined as quoted market prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; and Level 3, defined as unobservable inputs that are not corroborated by market data.

We use valuation techniques that maximize the use of market prices and observable inputs and minimize the use of unobservable inputs. In measuring the fair value of our financial assets and liabilities, we rely on market data or assumptions that we believe market participants would use in pricing an asset or a liability.

Assets and Liabilities Accounted for at Fair Value

Our financial instruments include cash and cash equivalents, accounts receivable, restricted investment securities held in trust on deposit with various banks as collateral for our obligations relative to our landfill final capping, closure and post-closure costs, interest rate swaps, trade payables and long-term debt. The carrying values of cash and cash equivalents, accounts receivable and trade payables approximate their respective fair values due to their short-term nature. The fair value of restricted investment securities held in trust, which are valued using quoted market prices, are included as restricted assets in the Level 1 tier below. The fair value of the interest rate swaps included in the Level 2 tier below is calculated using discounted cash flow valuation methodologies based upon the one month LIBOR yield curves that are observable at commonly quoted intervals for the full term of the swaps.

Recurring Fair Value Measurements

Summaries of our financial assets and liabilities that are measured at fair value on a recurring basis follow:


	Fair Value Measurement at September 30, 2019 Using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Restricted investment securities - landfill closure	$	1,410	$	—	$	—



Liabilities:
Interest rate swaps	$	—	$	6,084	$	—


	Fair Value Measurement at December 31, 2018 Using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:


Restricted investment securities - landfill closure	$	1,248	$	—	$	—
Interest rate swaps	—		820		—
	$	1,248	$	820	$	—
Liabilities:
Interest rate swaps	$	—	$	1,942	$	—

Fair Value of Debt

As of September 30, 2019, the fair value of our fixed rate debt, including our FAME Bonds 2005R-3, FAME Bonds 2015R-1, FAME Bonds 2015R-2, Vermont Bonds, New York Bonds 2014, New York Bonds 2014R-2 and New Hampshire Bonds was approximately $131,557 and the carrying value was $122,000. The fair value of the FAME Bonds 2005R-3, the FAME Bonds 2015R-1, the FAME Bonds 2015R-2, the Vermont Bonds, the New York Bonds 2014, the New York Bonds 2014R-2 and the New Hampshire Bonds is considered to be Level 2 within the fair value hierarchy as the fair value is determined using market approach pricing provided by a third-party that utilizes pricing models and pricing systems, mathematical tools and judgment to determine the evaluated price for the security based on the market information of each of the bonds or securities with similar characteristics.

As of September 30, 2019, the carrying value of our Term Loan Facility was $350,000 and the carrying value of our Revolving Credit Facility was $43,400. Their fair values are based on current borrowing rates for similar types of borrowing arrangements, or Level 2 inputs, and approximate their carrying values.

Although we have determined the estimated fair value amounts of FAME Bonds 2005R-3, FAME Bonds 2015R-1, FAME Bonds 2015R-2, Vermont Bonds, New York Bonds 2014, New York Bonds 2014R-2 and New Hampshire Bonds using available market information and commonly accepted valuation methodologies, a change in available market information, and/or the use of different assumptions and/or estimation methodologies could have a material effect on the estimated fair values. These amounts have not been revalued, and current estimates of fair value could differ significantly from the amounts presented.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXESDuring the nine months ended September 30, 2019, we recognized a $(2,137) deferred tax benefit due to a reduction of the valuation allowance. In determining the need for a valuation allowance, we have assessed the available means of recovering deferred tax assets, including the existence of reversing temporary differences. The valuation allowance decreased due to the recognition of additional reversing temporary differences from the $2,137 deferred tax liability recorded through goodwill related to an acquisition of a company in May 2019. The $2,137 deferred tax liability related to the acquisition was based on the impact of temporary differences between the amounts of assets and liabilities recognized for financial reporting purposes and such amounts recognized for income tax purposes.During the three months ended September 30, 2019, we recognized a $(297) deferred tax benefit due to a reduction of the deferred tax liability related to indefinite lived assets. During the quarter, the financial statement value of indefinite lived goodwill was reduced as a result of a settlement of an acquisition contingency that pre-dated the effective date of ASC 805, which resulted in a reduction of the related deferred tax liability.

SEGMENT REPORTING

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

SEGMENT REPORTING

We report selected information about operating segments in a manner consistent with that used for internal management reporting. We classify our solid waste operations on a geographic basis through regional operating segments, our Western and Eastern regions. Revenues associated with our solid waste operations are derived mainly from solid waste collection and disposal, landfill, landfill gas-to-energy, transfer and recycling services in the northeastern United States. Our revenues in the Recycling segment are derived from municipalities and customers in the form of processing fees, tipping fees and commodity sales. Organics services, ancillary operations, along with major account and industrial services are included in our Other segment.

Three Months Ended September 30, 2019


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	59,675	$	15,156	$	6,386	$	2,121	$	209,123
Western	92,871		26,645		12,620		15,148		596,765
Recycling	10,726		2,486		1,028		145		57,216
Other	35,275		718		906		1,071		72,676
Eliminations	—		(45,005)		—		—		—
	$	198,547	$	—	$	20,940	$	18,485	$	935,780

Three Months Ended September 30, 2018


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	56,006	$	14,557	$	7,267	$	15,222	$	180,896
Western	74,425		20,578		8,844		13,927		402,931
Recycling	10,877		1,773		1,131		(516)		48,995
Other	31,524		455		960		251		70,026
Eliminations	—		(37,363)		—		—		—
	$	172,832	$	—	$	18,202	$	28,884	$	702,848

Nine Months Ended September 30, 2019


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	163,748	$	40,606	$	18,014	$	5,722	$	209,123
Western	251,860		70,960		34,279		30,849		596,765
Recycling	32,006		6,820		2,975		(1,010)		57,216
Other	102,056		1,911		2,876		2,910		72,676
Eliminations	—		(120,297)		—		—		—
Total	$	549,670	$	—	$	58,144	$	38,471	$	935,780

Nine Months Ended September 30, 2018


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	154,099	$	40,432	$	20,276	$	17,675	$	180,896
Western	210,208		59,898		25,226		33,104		402,931
Recycling	30,634		4,697		3,228		(7,933)		48,995
Other	90,995		1,374		2,842		2,025		70,026
Eliminations	—		(106,401)		—		—		—
Total	$	485,936	$	—	$	51,572	$	44,871	$	702,848

A summary of our revenues attributable to services provided follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Collection	$	98,966	$	79,611	$	274,111	$	220,650
Disposal	50,552		48,737		134,746		136,217
Power generation	808		920		2,655		4,014
Processing	2,640		2,079		5,426		5,847
Solid waste operations	152,966		131,347		416,938		366,728
Organics	14,166		13,413		42,668		40,259
Customer solutions	20,689		17,195		58,058		48,315
Recycling	10,726		10,877		32,006		30,634
Total revenues	$	198,547	$	172,832	$	549,670	$	485,936

ACCOUNTING CHANGES (Policies)

9 Months Ended

Sep. 30, 2019

Accounting Changes and Error Corrections [Abstract]

Basis of Accounting

Casella Waste Systems, Inc. (“Parent”), and its consolidated subsidiaries (collectively, “we”, “us” or “our”), is a regional, vertically integrated solid waste services company that provides collection, transfer, disposal, landfill, landfill gas-to-energy, recycling and organics services in the northeastern United States. We market recyclable metals, aluminum, plastics, paper, and corrugated cardboard, which have been processed at our recycling facilities, as well as recyclables purchased from third-parties. We manage our solid waste operations on a geographic basis through two regional operating segments, the Eastern and Western regions, each of which provides a full range of solid waste services, and our larger-scale recycling and commodity brokerage operations through our Recycling segment. Organics services, ancillary operations, along with major account and industrial services are included in our Other segment.

The accompanying unaudited consolidated financial statements, which include the accounts of the Parent and our wholly-owned subsidiaries, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). All significant intercompany accounts and transactions are eliminated in consolidation. Investments in entities in which we do not have a controlling financial interest are accounted for under either the equity method or the cost method of accounting, as appropriate. Our significant accounting policies are more fully discussed in Item 8 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2018, which was filed with the SEC on February 22, 2019.

Use of Estimates

Preparation of our consolidated financial statements in accordance with GAAP requires management to make certain estimates and assumptions. These estimates and assumptions affect the accounting for and recognition and disclosure of assets, liabilities, equity, revenues and expenses. We must make these estimates and assumptions because certain information that we use is dependent on future events, cannot be calculated with a high degree of precision given the available data, or simply cannot be readily calculated. In the opinion of management, these consolidated financial statements include all adjustments, which include normal recurring and nonrecurring adjustments, necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented. The results for the three and nine months ended September 30, 2019 may not be indicative of the results for any other interim period or the entire fiscal year. The consolidated financial statements presented herein should be read in conjunction with our audited consolidated financial statements included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2018.

Subsequent Events

We have evaluated subsequent events or transactions that have occurred after the consolidated balance sheet date of September 30, 2019 through the date of filing of the consolidated financial statements with the SEC on this Quarterly Report on Form 10-Q. We have determined that, except as disclosed, there are no subsequent events that require disclosure in this Quarterly Report on Form 10-Q.

Accounting Standards that are Adopted and Pending Adoption

Standard

Description

Effect on the Financial Statements or Other
Significant Matters

Accounting standards adopted effective January 1, 2019

ASU No. 2016-02, as amended through March 2019: Leases (Topic 842)

Standard

Description

Effect on the Financial Statements or Other
Significant Matters

Accounting standards issued pending adoption

ASU No. 2017-04: Intangibles - Goodwill and Other (Topic 350)

Revenue Recognition

Payments to customers that are not in exchange for a distinct good or service are recorded as a reduction of revenues. Rebates to certain customers associated with payments for recycled or organic materials that are received and subsequently processed and sold to other third-parties amounted to $1,027 and $3,474 in the three and nine months ended September 30, 2019, respectively, and $1,648 and $4,732 in the three and nine months ended September 30, 2018, respectively. Rebates are generally recorded as a reduction of revenues upon the sale of such materials, or upon receipt of the recycled materials at our facilities. These payments were previously recorded as a cost of operations. We did not record any revenues in the three and nine months ended September 30, 2019 and September 30, 2018 from performance obligations satisfied in previous periods. Contract receivables, which are included in Accounts receivable, net are recorded when billed or when related revenue is earned, if earlier, and represent claims against third-parties that will be settled in cash. Accounts receivable, net includes gross receivables from contracts of $90,291 and $73,500 as of September 30, 2019 and December 31, 2018, respectively. Certain customers are billed in advance and, accordingly, recognition of the related revenues is deferred as a contract liability until the services are provided and control transferred to the customer.

Leases

Accrued Final Capping, Closure and Post Closure

Commitments and Contingencies

Fair Value of Financial Instruments

Assets and Liabilities Accounted for at Fair Value

Segment Reporting

ACCOUNTING CHANGES (Tables)

9 Months Ended

Sep. 30, 2019

Accounting Changes and Error Corrections [Abstract]

Schedule of New Accounting Pronouncements and Changes in Accounting Principles

Standard

Description

Effect on the Financial Statements or Other
Significant Matters

Accounting standards adopted effective January 1, 2019

ASU No. 2016-02, as amended through March 2019: Leases (Topic 842)

Standard

Description

Effect on the Financial Statements or Other
Significant Matters

Accounting standards issued pending adoption

ASU No. 2017-04: Intangibles - Goodwill and Other (Topic 350)

REVENUE RECOGNITION (Tables)

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

A table of revenues disaggregated by service line and timing of revenue recognition by operating segment for each of the three and nine months ended September 30, 2019 and 2018 follows:

Three Months Ended September 30, 2019


	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	41,868	$	59,323	$	—	$	—	$	101,191
Landfill	5,414		20,018		—		—		25,432
Transfer	12,247		9,694		—		—		21,941
Customer solutions	—		—		—		20,689		20,689


Recycling	4		461		10,726		—		11,191


Organics	—		—		—		14,166		14,166
Transportation	—		2,709		—		420		3,129


Landfill gas-to-energy	142		666		—		—		808
Total revenues	$	59,675	$	92,871	$	10,726	$	35,275	$	198,547

Transferred at a point-in-time	$	36	$	186	$	4,592	$	1,156	$	5,970
Transferred over time	59,639		92,685		6,134		34,119		192,577
Total revenues	$	59,675	$	92,871	$	10,726	$	35,275	$	198,547

Three Months Ended September 30, 2018


	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	36,392	$	44,452	$	—	$	—	$	80,844
Landfill	8,336		18,764		—		—		27,100
Transfer	11,001		7,290		—		—		18,291
Customer solutions	—		—		—		17,195		17,195


Recycling	5		875		10,877		—		11,757


Organics	—		—		—		13,413		13,413
Transportation	—		2,396		—		916		3,312


Landfill gas-to-energy	272		648		—		—		920
Total revenues	$	56,006	$	74,425	$	10,877	$	31,524	$	172,832

Transferred at a point-in-time	$	128	$	233	$	7,436	$	1,138	$	8,935
Transferred over time	55,878		74,192		3,441		30,386		163,897
Total revenues	$	56,006	$	74,425	$	10,877	$	31,524	$	172,832

Nine Months Ended September 30, 2019



	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	115,363	$	163,070	$	—	$	—	$	278,433
Landfill	14,558		54,341		—		—		68,899
Transfer	33,157		23,566		—		—		56,723
Customer solutions	—		—		—		58,058		58,058


Recycling	5		1,243		32,006		—		33,254


Organics	—		—		—		42,668		42,668
Transportation	—		7,650		—		1,330		8,980


Landfill gas-to-energy	665		1,990		—		—		2,655
Total revenues	$	163,748	$	251,860	$	32,006	$	102,056	$	549,670

Transferred at a point-in-time	$	123	$	673	$	15,768	$	2,877	$	19,441
Transferred over time	163,625		251,187		16,238		99,179		530,229
Total revenues	$	163,748	$	251,860	$	32,006	$	102,056	$	549,670

Nine Months Ended September 30, 2018


	Eastern		Western		Recycling		Other		Total Revenues
Collection	$	101,544	$	121,804	$	—	$	—	$	223,348
Landfill	22,179		49,504		—		—		71,683
Transfer	29,305		20,907		—		—		50,212
Customer solutions	—		—		—		48,315		48,315


Recycling	—		3,271		30,634		—		33,905


Organics	—		—		—		40,259		40,259
Transportation	—		11,779		—		2,421		14,200


Landfill gas-to-energy	1,071		2,943		—		—		4,014
Total revenues	$	154,099	$	210,208	$	30,634	$	90,995	$	485,936

Transferred at a point-in-time	$	500	$	847	$	20,311	$	3,219	$	24,877
Transferred over time	153,599		209,361		10,323		87,776		461,059
Total revenues	$	154,099	$	210,208	$	30,634	$	90,995	$	485,936

BUSINESS COMBINATIONS (Tables)

9 Months Ended

Sep. 30, 2019

Business Combinations [Abstract]

Summary of Purchase Price Paid for Acquisitions

A summary of the purchase price paid for these acquisitions and the allocation of the purchase price for these acquisitions follows:


	Nine Months Ended September 30,
	2019		2018
Purchase Price:
Cash used in acquisitions, net of cash acquired	$	71,038	$	57,824
Notes payable	2,714		—
Common stock	—		4,258
Other non-cash consideration	5,470		—
Contingent consideration and holdbacks	1,755		4,996
Total	80,977		67,078
Allocated as follows:
Current assets	1,935		2,968
Other non-current assets	367		—
Land	2,487		—
Buildings	5,422		7,539
Equipment	20,592		11,520
Intangible assets	31,171		20,300
Other liabilities, net	(3,040)		(2,443)
Deferred tax liability	(2,137)		(1,230)
Fair value of assets acquired and liabilities assumed	56,797		38,654
Excess purchase price allocated to goodwill	$	24,180	$	28,424

Schedule of Unaudited Pro forma Combined Information

Unaudited pro forma combined information that shows our operational results as though each acquisition completed since the beginning of the prior fiscal year had occurred as of January 1, 2018 is as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Revenues	$	204,293	$	196,686	$	579,390	$	561,912
Operating income	$	19,369	$	31,505	$	42,321	$	53,051
Net income	$	12,905	$	23,794	$	24,810	$	24,745

Basic earnings per share attributable to common stockholders:
Weighted average common shares outstanding	47,690		42,779		47,029		42,605
Basic earnings per common share	$	0.27	$	0.56	$	0.53	$	0.58
Diluted earnings per share attributable to common stockholders:
Weighted average shares outstanding	48,361		44,175		47,660		43,938
Diluted earnings per common share	$	0.27	$	0.54	$	0.52	$	0.56

LEASES (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Schedule of Lease Costs and Other Lease Information

A schedule of lease costs and other lease information follows:


	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Lease cost:
Amortization of right-of-use assets	$	593	$	1,505
Interest expense	213		555
Fixed lease cost - vehicles, equipment and property	2,351		7,271
Fixed lease cost - landfill operating leases	1,957		5,580
Fixed lease cost	4,308		12,851
Short-term lease cost	853		2,261
Variable lease cost	329		712
Total lease cost	$	6,296	$	17,884

Other information:
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows for finance leases	$	666	$	1,870
Operating cash flows for operating leases	$	2,963	$	9,837
Right-of-use assets obtained in exchange for new finance lease liabilities	$	—	$	6,857
Right-of-use assets obtained in exchange for new operating lease liabilities	$	831	$	1,419

			September 30, 2019
Weighted-average remaining lease term - finance leases (years)			6.7
Weighted-average remaining lease term - operating leases (years)			12.0
Weighted-average discount rate - finance leases			5.2		%
Weighted-average discount rate - operating leases			5.2		%

Schedule of Estimated Minimum Future Finance Lease Obligations

Estimated minimum future lease obligations are as follows:


	Operating Leases		Finance Leases
Fiscal year ending December 31, 2019	$	3,792	$	799
Fiscal year ending December 31, 2020	13,218		3,872
Fiscal year ending December 31, 2021	10,870		3,336
Fiscal year ending December 31, 2022	8,494		2,740
Fiscal year ending December 31, 2023	6,652		2,572
Thereafter	69,323		6,924
Total lease payments	112,349		20,243
Less: interest expense	(30,857)		(3,733)
Lease liability balance	$	81,492	$	16,510

Schedule of Estimated Minimum Future Operating Lease Obligations

Estimated minimum future lease obligations are as follows:


	Operating Leases		Finance Leases
Fiscal year ending December 31, 2019	$	3,792	$	799
Fiscal year ending December 31, 2020	13,218		3,872
Fiscal year ending December 31, 2021	10,870		3,336
Fiscal year ending December 31, 2022	8,494		2,740
Fiscal year ending December 31, 2023	6,652		2,572
Thereafter	69,323		6,924
Total lease payments	112,349		20,243
Less: interest expense	(30,857)		(3,733)
Lease liability balance	$	81,492	$	16,510

GOODWILL AND INTANGIBLE ASSETS (Tables)

9 Months Ended

Sep. 30, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Goodwill Activity

A summary of the activity and balances related to goodwill by reporting segment is as follows:


	December 31, 2018		Acquisitions		Other (1)		September 30, 2019
Eastern region	$	28,154	$	2,566	$	—	$	30,720
Western region	120,536		21,614		(2,619)		139,531
Recycling	12,315		—		—		12,315
Other	1,729		—		—		1,729
Total	$	162,734	$	24,180	$	(2,619)	$	184,295

(1)Relates to the unregistered sale of Class A common stock that was previously held in escrow and released to us for liquidation . See Note 10, Stockholders' Equity for additional disclosure.

Summary of Intangible Assets by Intangible Asset Type

A summary of intangible assets by intangible asset type follows:


	Covenants Not-to-Compete		Client Lists		Total
Balance, September 30, 2019
Intangible assets	$	26,162	$	71,122	$	97,284
Less accumulated amortization	(18,575)		(17,726)		(36,301)
	$	7,587	$	53,396	$	60,983


	Covenants Not-to-Compete		Client Lists		Total
Balance, December 31, 2018
Intangible assets	$	21,750	$	44,363	$	66,113
Less accumulated amortization	(17,584)		(13,762)		(31,346)
	$	4,166	$	30,601	$	34,767

Summary of Intangible Amortization Expense Estimated

A summary of intangible amortization expense estimated for the five fiscal years following the fiscal year ended December 31, 2018 and thereafter follows:



Estimated Future Amortization Expense as of September 30, 2019
Fiscal year ending December 31, 2019	$	2,264
Fiscal year ending December 31, 2020	$	8,222
Fiscal year ending December 31, 2021	$	6,826
Fiscal year ending December 31, 2022	$	6,188
Fiscal year ending December 31, 2023	$	5,993
Thereafter	$	31,490

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE (Tables)

9 Months Ended

Sep. 30, 2019

Asset Retirement Obligation Disclosure [Abstract]

Summary of Changes to Accrued Capping, Closure and Post-Closure Liabilities

A summary of the changes to accrued final capping, closure and post-closure liabilities follows:


	Nine Months Ended September 30,
	2019		2018
Beginning balance	$	73,075	$	62,290
Obligations incurred	1,901		2,874
Revision in estimates (1)	—		1,492
Accretion expense	4,742		4,175

Obligations settled (2)	(7,099)		(2,310)
Ending balance	$	72,619	$	68,521

(2)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.

LONG-TERM DEBT (Tables)

9 Months Ended

Sep. 30, 2019

Debt And Derivatives Disclosure [Abstract]

Summary of Long-term Debt and Finance Leases by Debt Instrument

A summary of long-term debt and finance leases by debt instrument follows:


	September 30, 2019		December 31, 2018
Senior Secured Credit Facility:
Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.75%	$	43,400	$	69,600
Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.75%	350,000		350,000

Tax-Exempt Bonds:
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014 ("New York Bonds 2014") due December 2044 - fixed rate interest period through 2019; bearing interest at 3.75%	25,000		25,000
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 ("New York Bonds 2014R-2") due December 2044 - fixed rate interest period through 2026; bearing interest at 3.125%	15,000		15,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 ("FAME Bonds 2005R-3") due January 2025 - fixed rate interest period through 2025; bearing interest at 5.25%	25,000		25,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-1 ("FAME Bonds 2015R-1") due August 2035 - fixed rate interest period through 2025; bearing interest at 5.125%	15,000		15,000
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2 ("FAME Bonds 2015R-2") due August 2035 - fixed rate interest period through 2025; bearing interest at 4.375%	15,000		15,000
Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 ("Vermont Bonds") due April 2036 - fixed rate interest period through 2028; bearing interest at 4.625%	16,000		16,000
Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 ("New Hampshire Bonds") due April 2029 - fixed rate interest period through September 2019; bore interest at 4.00%	11,000		11,000
Other:
Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2%	16,510		11,248
Notes payable maturing through June 2027; bearing interest at a weighted average of 3.5%	4,862		2,401
Principal amount of long-term debt and finance leases	536,772		555,249
Less—unamortized debt issuance costs (1)	9,226		10,950
Long-term debt and finance leases less unamortized debt issuance costs	527,546		544,299
Less—current maturities of long-term debt and finance leases	3,571		2,298
	$	523,975	$	542,001

(1)A summary of unamortized debt issuance costs by debt instrument follows:


	September 30, 2019		December 31, 2018
Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility")	$	5,889	$	7,118
New York Bonds 2014	707		847
New York Bonds 2014R-2	405		450
FAME Bonds 2005R-3	453		517
FAME Bonds 2015R-1	569		622
FAME Bonds 2015R-2	436		493
Vermont Bonds	554		595
New Hampshire Bonds	213		308
	$	9,226	$	10,950

Summary of Cash Flow Hedges

A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows:


		Fair Value
	Balance Sheet Location	September 30, 2019		December 31, 2018
Interest rate swaps	Other current assets	$	—	$	338
Interest rate swaps	Other non-current assets	—		482
		$	—	$	820

Interest rate swaps	Other accrued liabilities	$	1,686	$	387
Interest rate swaps	Other long-term liabilities	4,398		1,555
		$	6,084	$	1,942

Interest rate swaps	Accumulated other comprehensive loss	$	(6,459)	$	(1,196)
Interest rate swaps - tax provision	Accumulated other comprehensive loss	(112)		(112)
		$	(6,571)	$	(1,308)

A summary of the amount of expense on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income (loss) into earnings follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Statement of Operations Location	(Expense) Income						(Expense) Income
Interest expense	$	(147)	$	(156)	$	(216)	$	(247)

COMMITMENTS AND CONTINGENCIES (Tables)

9 Months Ended

Sep. 30, 2019

Southbridge Landfill

Site Contingency [Line Items]

Summary of Environmental Liability

The changes to the environmental remediation liability associated with the Southbridge Landfill are as follows:



	Nine Months Ended September 30,
	2019		2018
Beginning balance	$	5,173	$	5,936
Accretion expense	94		116


Obligations settled (1)	(556)		(612)
Ending balance	$	4,711	$	5,440

(1)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.

Potsdam Environmental Remediation

Site Contingency [Line Items]

Summary of Environmental Liability

A summary of the changes to the environmental remediation liability associated with the Potsdam environmental remediation liability follows:



	Nine Months Ended September 30,
	2019		2018
Beginning balance	$	5,614	$	5,758



Obligations settled (1)	(1,764)		(98)
Ending balance	$	3,850	$	5,660

(1)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.

STOCKHOLDERS' EQUITY (Tables)

9 Months Ended

Sep. 30, 2019

Equity [Abstract]

Summary of Stock Option Activity

A summary of stock option activity follows:


	Stock Options (1)	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2018	669	$	6.37
Granted	—	$	—
Exercised	(571)	$	5.88
Forfeited	—	$	—
Outstanding, September 30, 2019	98	$	9.20	6.1	$	3,311
Exercisable, September 30, 2019	98	$	9.20	6.1	$	3,311

Summary of Restricted Stock, Restricted Stock Unit and Performance Stock Unit Activity

A summary of restricted stock, restricted stock unit and performance stock unit activity follows:


	Restricted Stock, Restricted Stock Units, and Performance Stock Units (1)	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2018	686	$	15.56
Granted	163	$	37.14
Class A Common Stock Vested	(217)	$	12.19
Forfeited	(7)	$	20.48
Outstanding, September 30, 2019	625	$	22.36	1.1	$	12,866
Unvested, September 30, 2019	950	$	21.90	1.0	$	19,998

Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Loss

A summary of the changes in the balances of each component of accumulated other comprehensive loss, net of tax follows:



	Interest Rate Swaps
Balance, December 31, 2018	$	(1,308)

Other comprehensive loss before reclassifications	(5,479)
Amounts reclassified from accumulated other comprehensive loss	216
Income tax provision related to items of other comprehensive loss	—
Net current-period other comprehensive loss	(5,263)
Balance, September 30, 2019	$	(6,571)

Summary of Reclassifications Out of Accumulated Other Comprehensive Loss

A summary of reclassifications out of accumulated other comprehensive loss, net of tax follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Details About Accumulated Other Comprehensive Loss Components	Amounts Reclassified Out of Accumulated Other Comprehensive Loss									Affected Line Item in the Consolidated Statements of Operations
Interest rate swaps	$	147	$	156	$	216	$	247	Interest expense
	147		156		216		247		Income before income taxes
	—		—		—		—		Provision (benefit) for income taxes
	$	147	$	156	$	216	$	247	Net income

EARNINGS PER SHARE (Tables)

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Summary of Numerator and Denominators Used in Computation of Earnings per Share

A summary of the numerator and denominators used in the computation of earnings per share follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Numerator:
Net income	$	12,386	$	22,302	$	22,587	$	20,096
Denominators:
Number of shares outstanding, end of period:
Class A common stock	46,792		41,932		46,792		41,932
Class B common stock	988		988		988		988
Shares to be issued - acquisition	36		—		36		—
Unvested restricted stock	(9)		(32)		(9)		(32)
Effect of weighted average shares outstanding	(117)		(109)		(778)		(283)
Basic weighted average common shares outstanding	47,690		42,779		47,029		42,605
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards	671		1,396		631		1,333
Diluted weighted average common shares outstanding	48,361		44,175		47,660		43,938
Anti-dilutive potentially issuable shares	2		—		2		2

OTHER ITEMS AND CHARGES (Tables)

9 Months Ended

Sep. 30, 2019

Unusual or Infrequent Items, or Both [Abstract]

Summary of Environmental Exit Costs by Cost


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018



Charlton settlement charge (1)	$	—	$	—	$	—	$	1,216
Legal and other costs (2)	625		502		2,097		1,044
Recovery on insurance settlement (3)	—		(10,000)		—		(10,000)

Southbridge Landfill closure charge (settlement), net	$	625	$	(9,498)	$	2,097	$	(7,740)

(1)We established a reserve associated with settlement of the Town of Charlton's claim against us. See Note 9, Commitments and Contingencies for additional disclosure.

(2)We incurred legal costs as well as other costs associated with various matters as part of the Southbridge Landfill closure. See Note 9, Commitments and Contingencies for additional disclosure.

(3)We recorded a recovery on an environmental insurance settlement associated with the Southbridge Landfill closure. See Note 9, Commitments and Contingencies for additional disclosure.

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities Measured at Fair Value

Summaries of our financial assets and liabilities that are measured at fair value on a recurring basis follow:


	Fair Value Measurement at September 30, 2019 Using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Restricted investment securities - landfill closure	$	1,410	$	—	$	—



Liabilities:
Interest rate swaps	$	—	$	6,084	$	—


	Fair Value Measurement at December 31, 2018 Using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:


Restricted investment securities - landfill closure	$	1,248	$	—	$	—
Interest rate swaps	—		820		—
	$	1,248	$	820	$	—
Liabilities:
Interest rate swaps	$	—	$	1,942	$	—

SEGMENT REPORTING (Tables)

9 Months Ended

Sep. 30, 2019

Segment Reporting [Abstract]

Summary of Segment Reporting Information by Segment

Three Months Ended September 30, 2019


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	59,675	$	15,156	$	6,386	$	2,121	$	209,123
Western	92,871		26,645		12,620		15,148		596,765
Recycling	10,726		2,486		1,028		145		57,216
Other	35,275		718		906		1,071		72,676
Eliminations	—		(45,005)		—		—		—
	$	198,547	$	—	$	20,940	$	18,485	$	935,780

Three Months Ended September 30, 2018


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	56,006	$	14,557	$	7,267	$	15,222	$	180,896
Western	74,425		20,578		8,844		13,927		402,931
Recycling	10,877		1,773		1,131		(516)		48,995
Other	31,524		455		960		251		70,026
Eliminations	—		(37,363)		—		—		—
	$	172,832	$	—	$	18,202	$	28,884	$	702,848

Nine Months Ended September 30, 2019


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	163,748	$	40,606	$	18,014	$	5,722	$	209,123
Western	251,860		70,960		34,279		30,849		596,765
Recycling	32,006		6,820		2,975		(1,010)		57,216
Other	102,056		1,911		2,876		2,910		72,676
Eliminations	—		(120,297)		—		—		—
Total	$	549,670	$	—	$	58,144	$	38,471	$	935,780

Nine Months Ended September 30, 2018


Segment	Outside revenues		Inter-company revenues		Depreciation and amortization		Operating income (loss)		Total assets
Eastern	$	154,099	$	40,432	$	20,276	$	17,675	$	180,896
Western	210,208		59,898		25,226		33,104		402,931
Recycling	30,634		4,697		3,228		(7,933)		48,995
Other	90,995		1,374		2,842		2,025		70,026
Eliminations	—		(106,401)		—		—		—
Total	$	485,936	$	—	$	51,572	$	44,871	$	702,848

Summary of Revenue Attributable to Services

A summary of our revenues attributable to services provided follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2019		2018		2019		2018
Collection	$	98,966	$	79,611	$	274,111	$	220,650
Disposal	50,552		48,737		134,746		136,217
Power generation	808		920		2,655		4,014
Processing	2,640		2,079		5,426		5,847
Solid waste operations	152,966		131,347		416,938		366,728
Organics	14,166		13,413		42,668		40,259
Customer solutions	20,689		17,195		58,058		48,315
Recycling	10,726		10,877		32,006		30,634
Total revenues	$	198,547	$	172,832	$	549,670	$	485,936

BASIS OF PRESENTATION (Details)	9 Months Ended
BASIS OF PRESENTATION (Details)	Sep. 30, 2019 regional_operating_segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of regional operating segments	2

REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 198,547	$ 172,832	$ 549,670	$ 485,936
Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	5,970	8,935	19,441	24,877
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	192,577	163,897	530,229	461,059
Collection
Disaggregation of Revenue [Line Items]
Total revenues	101,191	80,844	278,433	223,348
Landfill
Disaggregation of Revenue [Line Items]
Total revenues	25,432	27,100	68,899	71,683
Transfer
Disaggregation of Revenue [Line Items]
Total revenues	21,941	18,291	56,723	50,212
Customer solutions
Disaggregation of Revenue [Line Items]
Total revenues	20,689	17,195	58,058	48,315
Recycling
Disaggregation of Revenue [Line Items]
Total revenues	11,191	11,757	33,254	33,905
Organics
Disaggregation of Revenue [Line Items]
Total revenues	14,166	13,413	42,668	40,259
Transportation
Disaggregation of Revenue [Line Items]
Total revenues	3,129	3,312	8,980	14,200
Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	808	920	2,655	4,014
Eastern
Disaggregation of Revenue [Line Items]
Total revenues	59,675	56,006	163,748	154,099
Eastern \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	36	128	123	500
Eastern \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	59,639	55,878	163,625	153,599
Eastern \| Collection
Disaggregation of Revenue [Line Items]
Total revenues	41,868	36,392	115,363	101,544
Eastern \| Landfill
Disaggregation of Revenue [Line Items]
Total revenues	5,414	8,336	14,558	22,179
Eastern \| Transfer
Disaggregation of Revenue [Line Items]
Total revenues	12,247	11,001	33,157	29,305
Eastern \| Customer solutions
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Eastern \| Recycling
Disaggregation of Revenue [Line Items]
Total revenues	4	5	5	0
Eastern \| Organics
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Eastern \| Transportation
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Eastern \| Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	142	272	665	1,071
Western
Disaggregation of Revenue [Line Items]
Total revenues	92,871	74,425	251,860	210,208
Western \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	186	233	673	847
Western \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	92,685	74,192	251,187	209,361
Western \| Collection
Disaggregation of Revenue [Line Items]
Total revenues	59,323	44,452	163,070	121,804
Western \| Landfill
Disaggregation of Revenue [Line Items]
Total revenues	20,018	18,764	54,341	49,504
Western \| Transfer
Disaggregation of Revenue [Line Items]
Total revenues	9,694	7,290	23,566	20,907
Western \| Customer solutions
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Western \| Recycling
Disaggregation of Revenue [Line Items]
Total revenues	461	875	1,243	3,271
Western \| Organics
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Western \| Transportation
Disaggregation of Revenue [Line Items]
Total revenues	2,709	2,396	7,650	11,779
Western \| Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	666	648	1,990	2,943
Recycling
Disaggregation of Revenue [Line Items]
Total revenues	10,726	10,877	32,006	30,634
Recycling \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	4,592	7,436	15,768	20,311
Recycling \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	6,134	3,441	16,238	10,323
Recycling \| Collection
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Recycling \| Landfill
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Recycling \| Transfer
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Recycling \| Customer solutions
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Recycling \| Recycling
Disaggregation of Revenue [Line Items]
Total revenues	10,726	10,877	32,006	30,634
Recycling \| Organics
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Recycling \| Transportation
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Recycling \| Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Total revenues	35,275	31,524	102,056	90,995
Other \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	1,156	1,138	2,877	3,219
Other \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	34,119	30,386	99,179	87,776
Other \| Collection
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Other \| Landfill
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Other \| Transfer
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Other \| Customer solutions
Disaggregation of Revenue [Line Items]
Total revenues	20,689	17,195	58,058	48,315
Other \| Recycling
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Other \| Organics
Disaggregation of Revenue [Line Items]
Total revenues	14,166	13,413	42,668	40,259
Other \| Transportation
Disaggregation of Revenue [Line Items]
Total revenues	420	916	1,330	2,421
Other \| Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0

REVENUE RECOGNITION - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
REVENUE RECOGNITION - Narrative (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rebates	$ (198,547,000)	$ (172,832,000)	$ (549,670,000)	$ (485,936,000)
Revenue recognized fro performance obligation satisfied in previous period	0	0	0	0
Gross receivables from contracts	90,291,000		90,291,000		$ 73,500,000
Contract liabilities	2,812,000		2,812,000		$ 3,074,000
Adjustments \| Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rebates	$ 1,027,000	$ 1,648,000	$ 3,474,000	$ 4,732,000

BUSINESS COMBINATIONS - Additional Information (Details) - business	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Number of businesses acquired	8
Minimum
Business Acquisition [Line Items]
Useful life of finite lived intangible assets	5 years
Maximum
Business Acquisition [Line Items]
Useful life of finite lived intangible assets	10 years
Eastern \| Tuck-in Solid Waste Collection
Business Acquisition [Line Items]
Number of businesses acquired	3
Eastern \| Solid Waste Collection, Transfer and Processing
Business Acquisition [Line Items]
Number of businesses acquired		1
Western \| Tuck-in Solid Waste Collection
Business Acquisition [Line Items]
Number of businesses acquired	3
Western \| Solid Waste Collection, Transfer and Recycling
Business Acquisition [Line Items]
Number of businesses acquired	1
Western \| Solid Waste Hauling and Transfer Assets
Business Acquisition [Line Items]
Number of businesses acquired	1
Western \| Solid Waste Collection
Business Acquisition [Line Items]
Number of businesses acquired		3

BUSINESS COMBINATIONS - Summary of Purchase Price Paid for Acquisitions (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Purchase Price:
Cash used in acquisitions, net of cash acquired	$ 73,496	$ 58,176
Allocated as follows:
Excess purchase price allocated to goodwill	184,295		$ 162,734
Waste Collection Acquisitions
Purchase Price:
Cash used in acquisitions, net of cash acquired	71,038	57,824
Notes payable	2,714	0
Common stock	0	4,258
Other non-cash consideration	5,470	0
Contingent consideration and holdbacks	1,755	4,996
Total	80,977	67,078
Allocated as follows:
Current assets	1,935	2,968
Other non-current assets	367	0
Land	2,487	0
Buildings	5,422	7,539
Equipment	20,592	11,520
Intangible assets	31,171	20,300
Other liabilities, net	(3,040)	(2,443)
Deferred tax liability	(2,137)	(1,230)
Fair value of assets acquired and liabilities assumed	56,797	38,654
Excess purchase price allocated to goodwill	24,180	28,424
Common stock	$ 0	$ 4,258

BUSINESS COMBINATIONS - Schedule of Unaudited Pro forma Combined Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Combinations [Abstract]
Revenues	$ 204,293	$ 196,686	$ 579,390	$ 561,912
Operating income	19,369	31,505	42,321	53,051
Net income	$ 12,905	$ 23,794	$ 24,810	$ 24,745
Weighted average common shares outstanding, basic	47,690	42,779	47,029	42,605
Basic earnings per common share (in dollars per share)	$ 0.27	$ 0.56	$ 0.53	$ 0.58
Weighted average common shares outstanding, diluted	48,361	44,175	47,660	43,938
Diluted earnings per common share (in dollars per share)	$ 0.27	$ 0.54	$ 0.52	$ 0.56

LEASES - Schedule of Lease Costs and Other Lease Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Lease cost:
Amortization of right-of-use assets	$ 593	$ 1,505
Interest expense	213	555
Fixed lease cost	4,308	12,851
Short-term lease cost	853	2,261
Variable lease cost	329	712
Total lease cost	6,296	17,884
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows for finance leases	666	1,870
Operating cash flows for operating leases	2,963	9,837
Right-of-use assets obtained in exchange for new finance lease liabilities	0	6,857
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 831	$ 1,419
Weighted-average remaining lease term - finance leases (years)	6 years 8 months 12 days	6 years 8 months 12 days
Weighted-average remaining lease term - operating leases (years)	12 years	12 years
Weighted-average discount rate - finance leases	5.20%	5.20%	5.20%
Weighted-average discount rate - operating leases	5.20%	5.20%
Vehicles, equipment and property
Lease cost:
Fixed lease cost	$ 2,351	$ 7,271
Landfill
Lease cost:
Fixed lease cost	$ 1,957	$ 5,580

LEASES - Schedule of Estimated Minimum Future Lease Obligations (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Operating Leases
Fiscal year ending December 31, 2019	$ 3,792
Fiscal year ending December 31, 2020	13,218
Fiscal year ending December 31, 2021	10,870
Fiscal year ending December 31, 2022	8,494
Fiscal year ending December 31, 2023	6,652
Thereafter	69,323
Total lease payments	112,349
Less: interest expense	(30,857)
Lease liability balance	81,492
Finance Leases
Fiscal year ending December 31, 2019	799
Fiscal year ending December 31, 2020	3,872
Fiscal year ending December 31, 2021	3,336
Fiscal year ending December 31, 2022	2,740
Fiscal year ending December 31, 2023	2,572
Thereafter	6,924
Total lease payments	20,243
Less: interest expense	(3,733)
Lease liability balance	$ 16,510

GOODWILL AND INTANGIBLE ASSETS - Summary of Goodwill Activity (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 162,734
Acquisitions	24,180
Other	(2,619)
Goodwill, ending balance	184,295
Eastern
Goodwill [Roll Forward]
Goodwill, beginning balance	28,154
Acquisitions	2,566
Other	0
Goodwill, ending balance	30,720
Western
Goodwill [Roll Forward]
Goodwill, beginning balance	120,536
Acquisitions	21,614
Other	(2,619)
Goodwill, ending balance	139,531
Recycling
Goodwill [Roll Forward]
Goodwill, beginning balance	12,315
Acquisitions	0
Other	0
Goodwill, ending balance	12,315
Other
Goodwill [Roll Forward]
Goodwill, beginning balance	1,729
Acquisitions	0
Other	0
Goodwill, ending balance	$ 1,729

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets by Intangible Asset Type (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 97,284	$ 66,113
Less accumulated amortization	(36,301)	(31,346)
Intangible assets, net	60,983	34,767
Covenants Not-to-Compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets	26,162	21,750
Less accumulated amortization	(18,575)	(17,584)
Intangible assets, net	7,587	4,166
Client Lists
Finite-Lived Intangible Assets [Line Items]
Intangible assets	71,122	44,363
Less accumulated amortization	(17,726)	(13,762)
Intangible assets, net	$ 53,396	$ 30,601

GOODWILL AND INTANGIBLE ASSETS - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible amortization expense	$ 1,916	$ 714	$ 4,956	$ 1,848

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Amortization Expense Estimated (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Fiscal year ending December 31, 2019	$ 2,264
Fiscal year ending December 31, 2020	8,222
Fiscal year ending December 31, 2021	6,826
Fiscal year ending December 31, 2022	6,188
Fiscal year ending December 31, 2023	5,993
Thereafter	$ 31,490

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE - Summary of Changes to Accrued Capping, Closure and Post-Closure Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 73,075	$ 62,290
Obligations incurred	1,901	2,874
Revision in estimate	0	1,492
Accretion expense	4,742	4,175
Obligations settled	(7,099)	(2,310)
Ending balance	$ 72,619	$ 68,521

LONG-TERM DEBT - Summary of Components of Long-Term Debt and Capital Leases by Debt Instrument (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 536,772	$ 555,249
Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2%	16,510
Less - unamortized debt issuance costs	9,226	10,950
Long-term debt and finance leases less unamortized debt issuance costs	527,546	544,299
Less—current maturities of long-term debt and finance leases	3,571	2,298
Long-term debt and finance leases, less current portion	$ 523,975	$ 542,001
Weighted-average discount rate - finance leases	5.20%	5.20%
Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.75%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 43,400	$ 69,600
Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.75% \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%	1.75%
Secured Debt \| Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.75%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 350,000	$ 350,000
Secured Debt \| Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.75% \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%	1.75%
Credit Facility
Debt Instrument [Line Items]
Less - unamortized debt issuance costs	$ 5,889	$ 7,118
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014 ("New York Bonds 2014") due December 2044 - fixed rate interest period through 2019; bearing interest at 3.75%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	25,000	25,000
Less - unamortized debt issuance costs	$ 707	$ 847
Stated interest rate	3.75%	3.75%
New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 ("New York Bonds 2014R-2") due December 2044 - fixed rate interest period through 2026; bearing interest at 3.125%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 15,000	$ 15,000
Less - unamortized debt issuance costs	$ 405	$ 450
Stated interest rate	3.125%	3.125%
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 ("FAME Bonds 2005R-3") due January 2025 - fixed rate interest period through 2025; bearing interest at 5.25%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 25,000	$ 25,000
Less - unamortized debt issuance costs	$ 453	$ 517
Stated interest rate	5.25%	5.25%
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-1 ("FAME Bonds 2015R-1") due August 2035 - fixed rate interest period through 2025; bearing interest at 5.125%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 15,000	$ 15,000
Less - unamortized debt issuance costs	$ 569	$ 622
Stated interest rate	5.125%	5.125%
Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2 ("FAME Bonds 2015R-2") due August 2035 - fixed rate interest period through 2025; bearing interest at 4.375%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 15,000	$ 15,000
Less - unamortized debt issuance costs	$ 436	$ 493
Stated interest rate	4.375%	4.375%
Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 ("Vermont Bonds") due April 2036 - fixed rate interest period through 2028; bearing interest at 4.625%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 16,000	$ 16,000
Less - unamortized debt issuance costs	$ 554	$ 595
Stated interest rate	4.625%	4.625%
Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 ("New Hampshire Bonds") due April 2029 - fixed rate interest period through September 2019; bore interest at 4.00%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 11,000	$ 11,000
Less - unamortized debt issuance costs	$ 213	$ 308
Stated interest rate	4.00%	4.00%
Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases		$ 11,248
Notes payable maturing through June 2027; bearing interest at a weighted average of 3.5%
Debt Instrument [Line Items]
Principal amount of long-term debt and finance leases	$ 4,862	$ 2,401
Weighted average interest rate	3.50%	3.50%

LONG-TERM DEBT - Financing Activities (Details) - Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 ("New Hampshire Bonds") due April 2029 - fixed rate interest period through September 2019; bore interest at 4.00% - USD ($)	Oct. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Stated interest rate		4.00%	4.00%
Subsequent event
Debt Instrument [Line Items]
Aggregate principal amount	$ 11,000,000
Stated interest rate	2.95%

LONG-TERM DEBT - Credit Facility (Details)	3 Months Ended
LONG-TERM DEBT - Credit Facility (Details)	Sep. 30, 2019 USD ($)
Line of Credit
Debt Instrument [Line Items]
Debt instrument, term	5 years
Net leverage ratio	2.25
Line of credit facility, remaining borrowing capacity	$ 131,979,000
Line of Credit \| LIBOR
Debt Instrument [Line Items]
Floor interest rate received	1.25%
Line of Credit \| Maximum \| LIBOR
Debt Instrument [Line Items]
Floor interest rate received	1.75%
Secured Debt \| Term Loan Facility \| Line of Credit
Debt Instrument [Line Items]
Aggregate principal amount	$ 350,000,000
Revolving Credit Facility \| Revolving Credit Facility Due 2023 \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum	200,000,000
Letters of credit outstanding	24,621,000
Credit Facility
Debt Instrument [Line Items]
Additional revolver capacity	$ 125,000,000

LONG-TERM DEBT - Loss On Extinguishment of Debt (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Debt And Derivatives Disclosure [Abstract]
Loss on debt extinguishment	$ 0	$ 0	$ 0	$ 7,352

LONG-TERM DEBT - Cash Flow Hedges (Details) - Cash Flow Hedging - Interest Rate Derivative	Sep. 30, 2019 USD ($) interest_rate_derviative
Debt Instrument [Line Items]
Number of interest rate derivative agreements \| interest_rate_derviative	9
Notional amount \| $	$ 190,000,000
Weighted average percentage rate paid	2.54%

LONG-TERM DEBT - Schedule Of Cash Flow Hedges Related to Derivative Instruments On the Balance Sheet (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, assets	$ 0		$ 0		$ 820
Cash flow hedge derivatives, liabilities	6,084		6,084		1,942
Unrealized (loss) gain resulting from changes in fair value of derivative instruments	(774)	$ 863	(5,292)	$ 1,503
Other current assets \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, assets	0		0		338
Other non-current assets \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, assets	0		0		482
Other accrued liabilities \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, liabilities	1,686		1,686		387
Other long-term liabilities \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, liabilities	$ 4,398		4,398		1,555
Accumulated other comprehensive loss \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Unrealized (loss) gain resulting from changes in fair value of derivative instruments			(6,459)		(1,196)
Accumulated other comprehensive loss, interest rate swaps, tax provision			(112)		(112)
Accumulated other comprehensive loss			$ (6,571)		$ (1,308)

LONG-TERM DEBT - Schedule of Loss On Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ (147)	$ (156)	$ (216)	$ (247)
Designated as Hedging Instrument \| Interest rate swaps \| Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ (147)	$ (156)	$ (216)	$ (247)

COMMITMENTS AND CONTINGENCIES - Additional Information (Detail) numberOfPlantiffs in Thousands	Sep. 17, 2019 numberOfPlantiffs	Apr. 28, 2017 USD ($)	Sep. 30, 2019	Apr. 26, 2017 USD ($)	Jan. 29, 2016	Apr. 30, 2011 USD ($)	May 31, 2009 USD ($)	Dec. 20, 2000 a
Southbridge Landfill
Loss Contingencies [Line Items]
Risk free interest percentage rate			2.60%
Potsdam Environmental Remediation
Loss Contingencies [Line Items]
Risk free interest percentage rate			1.50%
Scrap yard and solid waste transfer station (in acres) \| a								25
Undiscounted costs preferred remedies						$ 12,130,000	$ 10,219,000
Remediation activities, participant share percentage					15.00%
21E Settlement and Water System Construction Funding Agreement \| Bonds
Loss Contingencies [Line Items]
Bond period		20 years
21E Settlement and Water System Construction Funding Agreement \| Bonds \| Maximum
Loss Contingencies [Line Items]
Anticipated cost		$ 5,000,000
Notice of Intent to Sue under the Resource Conservation and Recovery Act
Loss Contingencies [Line Items]
Estimate of possible loss				$ 5,000,000
Notice of Intent to Sue under the Resource Conservation and Recovery Act \| MADEP and Casella Waste Systems
Loss Contingencies [Line Items]
Estimate of possible loss				$ 10,000,000
Ontario County, New York Class Action Litigation
Loss Contingencies [Line Items]
Number of citizens seeking damages \| numberOfPlantiffs	1

COMMITMENTS AND CONTINGENCIES - Southbridge Landfill Environmental Remediation Liability (Details) - Southbridge Landfill - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 5,173	$ 5,936
Accretion expense	94	116
Obligations settled	(556)	(612)
Ending balance	$ 4,711	$ 5,440

COMMITMENTS AND CONTINGENCIES - Potsdam Environmental Remediation Liability (Detail) - Potsdam Environmental Remediation - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 5,614	$ 5,758
Obligations settled	(1,764)	(98)
Ending balance	$ 3,850	$ 5,660

STOCKHOLDERS' EQUITY - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2016
Limited Partners' Capital Account [Line Items]
Reduction of goodwill	$ 2,618		$ 2,618
Stock Options
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	0	$ 127	0	$ 377
Aggregate intrinsic value of options exercised	7,741		19,475
Restricted Stock, Restricted Stock Units And Performance Stock Units
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	1,858	2,007	$ 5,084	5,883
Restricted Stock \| Non Employee Director
Limited Partners' Capital Account [Line Items]
Options, vesting period			3 years
Restricted Stock and Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Fair value of stock awards vested	43		$ 7,764
Unrecognized stock-based compensation expense	3,852		3,852
Maximum \| Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	6,009		$ 6,009
Weighted average \| Restricted Stock and Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period			1 year 4 months 24 days
Weighted average \| Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period			10 months 24 days
2016 Plan
Limited Partners' Capital Account [Line Items]
Options granted, term			10 years
2016 Plan \| Minimum
Limited Partners' Capital Account [Line Items]
Options, vesting period			1 year
2016 Plan \| Maximum
Limited Partners' Capital Account [Line Items]
Options, vesting period			4 years
Amended and Restated 1997 Employee Stock Purchase Plan
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	$ 40	$ 34	$ 134	$ 106
Class A Common Stock \| 2016 Plan
Limited Partners' Capital Account [Line Items]
Common stock, authorized shares					2,250,000
Number of shares available for future grant	1,399,000		1,399,000
Class A Common Stock \| 2006 Incentive Plan
Limited Partners' Capital Account [Line Items]
Common stock, additional authorized shares					2,723,000
Public Stock Offering \| Class A Common Stock
Limited Partners' Capital Account [Line Items]
Number of shares issued			3,565,000
Price per share (in dollars per share)	$ 29.50		$ 29.50
Sale of stock, net proceeds			$ 100,446
Unregistered Sale \| Class A Common Stock
Limited Partners' Capital Account [Line Items]
Number of shares issued	59,000		59,000
Price per share (in dollars per share)	$ 44.15		$ 44.15
Sale of stock, net proceeds	$ 2,618		$ 2,618

STOCKHOLDERS' EQUITY - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Stock Options
Beginning balance, outstanding (in shares) \| shares	669
Granted (in shares) \| shares	0
Exercised (in shares) \| shares	(571)
Forfeited (in shares) \| shares	0
Ending balance, outstanding (in shares) \| shares	98
Exercisable at end of period (in shares) \| shares	98
Weighted Average Exercise Price
Beginning balance, outstanding (in dollars per share) \| $ / shares	$ 6.37
Granted (in dollars per share) \| $ / shares	0
Exercised (in dollars per share) \| $ / shares	5.88
Forfeited (in dollars per share) \| $ / shares	0
Ending balance, outstanding (in dollars per share) \| $ / shares	9.20
Exercisable at end of period (in dollars per share) \| $ / shares	$ 9.20
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Outstanding contractual term at end of period	6 years 1 month 6 days
Exercisable contractual term at end of period	6 years 1 month 6 days
Outstanding aggregate intrinsic value at end of period \| $	$ 3,311
Exercisable aggregate intrinsic value at end of period \| $	$ 3,311

STOCKHOLDERS' EQUITY - Summary of Restricted Stock, Restricted Stock Unit and Performance-based Stock Unit Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Restricted Stock, Restricted Stock Units And Performance Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding, beginning of period (in shares)	686
Granted (in shares)	163
Forfeited (in shares)	(7)
Outstanding, end of period (in shares)	625
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) \| $ / shares	$ 15.56
Granted (in dollars per share) \| $ / shares	37.14
Forfeited (in dollars per share) \| $ / shares	20.48
Outstanding at end of period (in dollars per share) \| $ / shares	$ 22.36
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term at end of period	1 year 1 month 6 days
Aggregate intrinsic value at end of period \| $	$ 12,866
Restricted Stock, Restricted Stock Units And Performance Stock Units \| Class A Common Stock
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Class A Common Stock Vested (in shares)	(217)
Weighted Average Grant Date Fair Value
Class A Common Stock Vested (in dollars per share) \| $ / shares	$ 12.19
Performance Stock Unit
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Percentage of attainment level	100.00%
Performance Stock Unit \| Class A Common Stock
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Number of additional shares	325
Unvested \| Restricted Stock, Restricted Stock Units And Performance Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding, end of period (in shares)	950
Weighted Average Grant Date Fair Value
Outstanding at end of period (in dollars per share) \| $ / shares	$ 21.90
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term at end of period	1 year
Aggregate intrinsic value at end of period \| $	$ 19,998

STOCKHOLDERS' EQUITY - Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ (15,832)
Ending balance	110,812
Interest Rate Swaps
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,308)
Other comprehensive loss	(5,479)
accumulated other comprehensive loss	216
Income tax provision related to items of other comprehensive loss	0
Net current-period other comprehensive loss	(5,263)
Ending balance	$ (6,571)

STOCKHOLDERS' EQUITY - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 6,235			$ 6,424			$ 18,849	$ 19,347
Income before income taxes	12,564			22,679			20,869	18,930
Provision (benefit) for income taxes	178			377			(1,718)	(1,166)
Net income	12,386	$ 11,915	$ (1,714)	22,302	$ 1,704	$ (3,910)	22,587	20,096
Interest rate swaps \| Interest Rate Swaps \| Amount Reclassified Out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	147			156			216	247
Income before income taxes	147			156			216	247
Provision (benefit) for income taxes	0			0			0	0
Net income	$ 147			$ 156			$ 216	$ 247

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

EARNINGS PER SHARE (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Numerator:
Net income	$ 12,386	$ 22,302	$ 22,587	$ 20,096
Denominators:
Shares to be issued - acquisition	36	0	36	0
Unvested restricted stock (in shares)	(9)	(32)	(9)	(32)
Effect of weighted average shares outstanding (in shares)	(117)	(109)	(778)	(283)
Weighted average common shares outstanding, basic	47,690	42,779	47,029	42,605
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards (in shares)	671	1,396	631	1,333
Weighted average common shares outstanding, diluted	48,361	44,175	47,660	43,938
Anti-dilutive potentially issuable shares	2	0	2	2
Class A Common Stock
Denominators:
Common stock, shares outstanding	46,792	41,932	46,792	41,932	41,944
Class B Common Stock
Denominators:
Common stock, shares outstanding	988	988	988	988	988

OTHER ITEMS AND CHARGES - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Unusual or Infrequent Items, or Both [Abstract]
Multiemployer pension plan withdrawal obligation	$ 3,194		$ 3,194
Withdrawal costs - multiemployer pension plan	3,591	$ 0	3,591	$ 0
Reversal of pension costs	397		$ 397
Contingent liability term			17 years
Multiemployer pension plan withdrawal obligation, undiscounted	4,224		$ 4,224
Estimated accumulated benefit obligation as complete withdrawal	18,511		18,511
Acquisition activities	1,097	581	2,237	719
Deferred cost write-offs		0		211
Contract settlement charge	0	0	0	2,100
Development project charge	$ 0	$ 0	$ 0	$ 311

OTHER ITEMS AND CHANGES - Summary of Environmental Exit Costs by Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Site Contingency [Line Items]
Southbridge Landfill closure charge (settlement), net	$ 625	$ (9,498)	$ 2,097	$ (7,740)
Southbridge Landfill
Site Contingency [Line Items]
Charlton settlement charge	0	0	0	1,216
Legal and other costs	625	502	2,097	1,044
Litigation Settlement, Amount Awarded from Other Party	0	(10,000)	0	(10,000)
Southbridge Landfill closure charge (settlement), net	$ 625	$ (9,498)	$ 2,097	$ (7,740)

FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring Fair Value Measurements (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
Restricted investment securities - landfill closure	$ 1,410	$ 1,248
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate swaps		0
Total		1,248
Liabilities:
Interest rate swaps	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Landfill
Assets:
Restricted investment securities - landfill closure	1,410	1,248
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Interest rate swaps		820
Total		820
Liabilities:
Interest rate swaps	6,084	1,942
Recurring \| Significant Other Observable Inputs (Level 2) \| Landfill
Assets:
Restricted investment securities - landfill closure	0	0
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Interest rate swaps		0
Total		0
Liabilities:
Interest rate swaps	0	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Landfill
Assets:
Restricted investment securities - landfill closure	$ 0	$ 0

FAIR VALUE OF FINANCIAL INSTRUMENTS - Additional Information (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Significant Other Observable Inputs (Level 2)
Debt Instrument [Line Items]
Carrying value of revolver debt	$ 43,400
Fair Value \| Fixed Rate Bonds
Debt Instrument [Line Items]
Fair value of fixed rate debt	131,557
Carrying Value \| Fixed Rate Bonds
Debt Instrument [Line Items]
Fair value of fixed rate debt	122,000
Carrying Value \| Term Loan Facility \| Secured Debt
Debt Instrument [Line Items]
Fair value of fixed rate debt	$ 350,000

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
INCOME TAXES (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2019	May 31, 2019
Income Tax Disclosure [Abstract]
Deferred tax (benefit)		$ (2,137)
Deferred tax liability, goodwill			$ 2,137
Deferred tax (benefit), indefinite lived assets	$ (297)

SEGMENT REPORTING - Summary of Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 198,547	$ 172,832	$ 549,670	$ 485,936
Depreciation and amortization	20,940	18,202	58,144	51,572
Operating Income (Loss)	18,485	28,884	38,471	44,871
Total assets	935,780		935,780		$ 732,410
Operating
Segment Reporting Information [Line Items]
Revenues	198,547	172,832	549,670	485,936
Depreciation and amortization	20,940	18,202	58,144	51,572
Operating Income (Loss)	18,485	28,884	38,471	44,871
Total assets	935,780	702,848	935,780	702,848
Operating \| Eastern
Segment Reporting Information [Line Items]
Revenues	59,675	56,006	163,748	154,099
Depreciation and amortization	6,386	7,267	18,014	20,276
Operating Income (Loss)	2,121	15,222	5,722	17,675
Total assets	209,123	180,896	209,123	180,896
Operating \| Western
Segment Reporting Information [Line Items]
Revenues	92,871	74,425	251,860	210,208
Depreciation and amortization	12,620	8,844	34,279	25,226
Operating Income (Loss)	15,148	13,927	30,849	33,104
Total assets	596,765	402,931	596,765	402,931
Operating \| Recycling
Segment Reporting Information [Line Items]
Revenues	10,726	10,877	32,006	30,634
Depreciation and amortization	1,028	1,131	2,975	3,228
Operating Income (Loss)	145	(516)	(1,010)	(7,933)
Total assets	57,216	48,995	57,216	48,995
Operating \| Other
Segment Reporting Information [Line Items]
Revenues	35,275	31,524	102,056	90,995
Depreciation and amortization	906	960	2,876	2,842
Operating Income (Loss)	1,071	251	2,910	2,025
Total assets	72,676	70,026	72,676	70,026
Inter-company revenues
Segment Reporting Information [Line Items]
Revenues	(45,005)	(37,363)	(120,297)	(106,401)
Inter-company revenues \| Eastern
Segment Reporting Information [Line Items]
Revenues	15,156	14,557	40,606	40,432
Inter-company revenues \| Western
Segment Reporting Information [Line Items]
Revenues	26,645	20,578	70,960	59,898
Inter-company revenues \| Recycling
Segment Reporting Information [Line Items]
Revenues	2,486	1,773	6,820	4,697
Inter-company revenues \| Other
Segment Reporting Information [Line Items]
Revenues	$ 718	$ 455	$ 1,911	$ 1,374

SEGMENT REPORTING - Summary of Revenues Attributable to Services Provided by Company (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue from External Customer [Line Items]
Revenues	$ 198,547	$ 172,832	$ 549,670	$ 485,936
Collection
Revenue from External Customer [Line Items]
Revenues	98,966	79,611	274,111	220,650
Disposal
Revenue from External Customer [Line Items]
Revenues	50,552	48,737	134,746	136,217
Power generation
Revenue from External Customer [Line Items]
Revenues	808	920	2,655	4,014
Processing
Revenue from External Customer [Line Items]
Revenues	2,640	2,079	5,426	5,847
Solid waste operations
Revenue from External Customer [Line Items]
Revenues	152,966	131,347	416,938	366,728
Organics
Revenue from External Customer [Line Items]
Revenues	14,166	13,413	42,668	40,259
Customer solutions
Revenue from External Customer [Line Items]
Revenues	20,689	17,195	58,058	48,315
Recycling
Revenue from External Customer [Line Items]
Revenues	$ 10,726	$ 10,877	$ 32,006	$ 30,634

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 18,000
AOCI Attributable to Parent [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (18,000)