Casella Waste Systems (CWST) 10-Q 2 Aug 19 2019 Q2 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	6 Months Ended
	Jun. 30, 2019	Jul. 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	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
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		46,598,767,000
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200,000

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 3,157	$ 4,007
Accounts receivable - trade, net of allowance for doubtful accounts	85,441	74,937
Refundable income taxes	2,602	2,254
Prepaid expenses	6,433	7,345
Inventory	7,054	6,542
Other current assets	699	2,008
Total current assets	105,386	97,093
Property, plant and equipment, net	406,636	404,577
Operating lease right-of-use assets	103,769
Goodwill	169,866	162,734
Intangible assets, net	43,347	34,767
Restricted assets	1,395	1,248
Cost method investments	11,264	11,264
Deferred income taxes	9,160	9,594
Other non-current assets	15,137	11,133
Total assets	865,960	732,410
CURRENT LIABILITIES:
Current maturities of long-term debt and finance leases	3,048	2,298
Accounts payable	61,731	57,289
Accrued payroll and related expenses	7,129	10,969
Accrued interest	2,209	2,415
Contract liabilities	2,644	3,074
Current accrued capping, closure and post-closure costs	9,159	11,633
Current operating lease liabilities	8,901
Other accrued liabilities	25,186	23,819
Total current liabilities	120,007	111,497
Long-term debt and finance leases, less current portion	483,892	542,001
Accrued capping, closure and post-closure costs, less current portion	65,380	61,442
Operating lease liabilities, less current portion	65,735
Deferred income taxes	2,657	2,519
Other long-term liabilities	32,092	30,783
COMMITMENTS AND CONTINGENCIES
Casella Waste Systems, Inc. stockholders' equity (deficit)
Additional paid-in capital	480,013	373,716
Accumulated deficit	(378,468)	(388,669)
Accumulated other comprehensive loss	(5,824)	(1,308)
Total stockholders' equity (deficit)	96,197	(15,832)
Total liabilities and stockholders' equity (deficit)	865,960	732,410
Class A Common Stock
Casella Waste Systems, Inc. stockholders' equity (deficit)
Common stock	466	419
Class B Common Stock
Casella Waste Systems, Inc. stockholders' equity (deficit)
Common stock	$ 10	$ 10

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019USD ($)vote$ / sharesshares	Dec. 31, 2018USD ($)vote$ / sharesshares
Statement of Financial Position [Abstract]
Accounts receivable - trade, allowance for doubtful accounts | $	$ 1,275	$ 931
Property, plant and equipment, accumulated depreciation and amortization | $	$ 817,367	$ 878,701
Class A Common Stock
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	100,000,000	100,000,000
Common stock, issued shares (in shares)	46,599,000	41,944,000
Common stock, outstanding shares (in shares)	46,599,000	41,944,000
Class B Common Stock
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	1,000,000	1,000,000
Common stock, issued shares (in shares)	988,000	988,000
Common stock, outstanding shares (in shares)	988,000	988,000
Votes per share held | vote	10	10

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues	$ 187,459	$ 165,649	$ 351,123	$ 313,104
Operating expenses:
Cost of operations	128,674	111,800	246,434	217,409
General and administration	22,145	20,793	44,887	41,820
Depreciation and amortization	19,715	17,386	37,204	33,370
Expense from acquisition activities and other items	464	349	1,140	349
Southbridge Landfill closure charge, net	917	172	1,472	1,759
Contract settlement charge	0	0	0	2,100
Development project charge	0	0	0	311
Total operating expenses	171,915	150,500	331,137	297,118
Operating income	15,544	15,149	19,986	15,986
Other expense (income):
Interest income	(105)	(79)	(222)	(108)
Interest expense	6,155	6,469	12,615	12,922
Loss on debt extinguishment	0	7,352	0	7,352
Other income	(496)	(342)	(711)	(431)
Other expense, net	5,554	13,400	11,682	19,735
Income (loss) before income taxes	9,990	1,749	8,304	(3,749)
(Benefit) provision for income taxes	(1,925)	45	(1,897)	(1,543)
Net income (loss)	$ 11,915	$ 1,704	$ 10,201	$ (2,206)
Basic earnings per share attributable to common stockholders:
Weighted average common shares outstanding (in shares)	47,464	42,661	46,693	42,516
Basic earnings per common shares (in dollars per share)	$ 0.25	$ 0.04	$ 0.22	$ (0.05)
Diluted earnings per share attributable to common stockholders:
Weighted average common shares outstanding (in shares)	48,221	43,916	47,424	42,516
Diluted earnings per common share (in dollars per share)	$ 0.25	$ 0.04	$ 0.22	$ (0.05)

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ 11,915	$ 1,704	$ 10,201	$ (2,206)
Hedging activity:
Interest rate swap settlements	(38)	(10)	(66)	(70)
Interest rate swap amounts reclassified into interest expense	44	38	69	91
Unrealized (loss) gain resulting from changes in fair value of derivative instruments	(2,965)	(145)	(4,519)	640
Other comprehensive (loss) income	(2,959)	(117)	(4,516)	661
Income tax (benefit) provision related to items of other comprehensive (loss) income	0	(32)	0	178
Other comprehensive (loss) income, net of tax	(2,959)	(85)	(4,516)	483
Comprehensive income (loss)	$ 8,956	$ 1,619	$ 5,685	$ (1,723)

CONSOLIDATED STATEMENT OF STOCK

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 StockCommon Stock	Class B Common Stock	Class B Common StockCommon 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
Issuances of Class A common stock (in shares)						402
Stock-based compensation	2,077	2,077
Net income (loss)	(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 (loss)	(2,206)
Hedging activity	483
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	41,765	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
Issuances of Class A common stock (in shares)						65
Stock-based compensation	2,121	2,121
Net income (loss)	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	41,765	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
Issuances of Class A common stock (in shares)						676
Stock-based compensation	1,431	1,431
Net income (loss)	(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 (loss)	10,201
Hedging activity	(4,516)
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	46,599	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
Issuances of Class A common stock (in shares)						347
Stock-based compensation	1,889	1,889
Net income (loss)	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	46,599	988	988

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash Flows from Operating Activities:
Net income (loss)	$ 10,201	$ (2,206)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	37,204	33,370
Operating lease right-of-use assets expense	4,921
Depletion of landfill operating lease obligations		4,993
Interest accretion on landfill and environmental remediation liabilities	3,579	2,862
Amortization of debt issuance costs and discount on long-term debt	1,149	1,290
Stock-based compensation	3,320	4,198
Gain on sale of property and equipment	(327)	(370)
Southbridge Landfill non-cash closure charge	179	1,273
Development project charge	0	311
Non-cash expense from acquisition activities and other items	(68)	211
Loss on debt extinguishment	0	(7,352)
Deferred income taxes	(1,565)	(725)
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(10,057)	(11,338)
Accounts payable	3,995	6,425
Prepaid expenses, inventories and other assets	(2,975)	2,617
Accrued expenses, contract liabilities and other liabilities	(14,928)	(2,184)
Net cash provided by operating activities	38,251	48,079
Cash Flows from Investing Activities:
Acquisitions, net of cash acquired	(27,687)	(19,369)
Additions to property, plant and equipment	(46,659)	(35,492)
Payments on landfill operating lease contracts	0	(3,467)
Proceeds from sale of property and equipment	363	469
Net cash used in investing activities	(73,983)	(57,859)
Cash Flows from Financing Activities:
Proceeds from long-term borrowings	41,400	528,900
Principal payments on long-term debt	(109,241)	(513,854)
Payments of debt issuance costs	0	(5,567)
Proceeds from the exercise of share based awards	2,277	398
Proceeds from the issuance of Class A Common Stock	100,446	0
Net cash provided by financing activities	34,882	9,877
Net (decrease) increase in cash and cash equivalents	(850)	97
Cash and cash equivalents, beginning of period	4,007	1,995
Cash and cash equivalents, end of period	3,157	2,092
Cash paid during the period for:
Interest	11,672	11,423
Income taxes, net of refunds	16	84
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Non-current assets obtained through long-term obligations	9,333	$ 3,267
Landfill
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Operating lease right-of-use assets expense	$ 3,623

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 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 six months ended June 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 June 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 there are no subsequent events that require disclosure in this Quarterly Report on Form 10-Q.

ACCOUNTING CHANGES

ACCOUNTING CHANGES	6 Months Ended
	Jun. 30, 2019
Accounting Changes and Error Corrections [Abstract]
ACCOUNTING CHANGES	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

REVENUE RECOGNITION	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION A table of revenues disaggregated by service line and timing of revenue recognition by operating segment for each of the three and six months ended June 30, 2019 and 2018 follows: Three Months Ended June 30, 2019 Eastern Western Recycling Other Total Revenues Collection $ 38,955 $ 54,151 $ — $ — $ 93,106 Landfill 5,427 18,855 — — 24,282 Transfer 11,923 8,597 — — 20,520 Customer solutions — — — 19,216 19,216 Recycling 577 341 10,514 — 11,432 Organics — — — 14,905 14,905 Transportation — 2,895 — 392 3,287 Landfill gas-to-energy 194 517 — — 711 Total revenues $ 57,076 $ 85,356 $ 10,514 $ 34,513 $ 187,459 Transferred at a point-in-time $ 52 $ 178 $ 5,051 $ 1,454 $ 6,735 Transferred over time 57,024 85,178 5,463 33,059 180,724 Total revenues $ 57,076 $ 85,356 $ 10,514 $ 34,513 $ 187,459 Three Months Ended June 30, 2018 Eastern Western Recycling Other Total Revenues Collection $ 34,625 $ 40,869 $ — $ — $ 75,494 Landfill 7,883 16,200 — — 24,083 Transfer 10,745 8,011 — — 18,756 Customer solutions — — — 15,950 15,950 Recycling — 1,445 9,600 — 11,045 Organics — — — 14,647 14,647 Transportation — 3,559 — 820 4,379 Landfill gas-to-energy 336 959 — — 1,295 Total revenues $ 53,589 $ 71,043 $ 9,600 $ 31,417 $ 165,649 Transferred at a point-in-time $ 181 $ 246 $ 5,618 $ 1,725 $ 7,770 Transferred over time 53,408 70,797 3,982 29,692 157,879 Total revenues $ 53,589 $ 71,043 $ 9,600 $ 31,417 $ 165,649 Six Months Ended June 30, 2019 Eastern Western Recycling Other Total Revenues Collection $ 72,919 $ 103,746 $ — $ — $ 176,665 Landfill 9,144 34,323 — — 43,467 Transfer 20,909 13,872 — — 34,781 Customer solutions — — — 37,370 37,370 Recycling 578 782 21,280 — 22,640 Organics — — — 28,501 28,501 Transportation — 4,942 — 910 5,852 Landfill gas-to-energy 523 1,324 — — 1,847 Total revenues $ 104,073 $ 158,989 $ 21,280 $ 66,781 $ 351,123 Transferred at a point-in-time $ 88 $ 487 $ 11,175 $ 1,721 $ 13,471 Transferred over time 103,985 158,502 10,105 65,060 337,652 Total revenues $ 104,073 $ 158,989 $ 21,280 $ 66,781 $ 351,123 Six Months Ended June 30, 2018 Eastern Western Recycling Other Total Revenues Collection $ 65,149 $ 77,353 $ — $ — $ 142,502 Landfill 13,843 30,740 — — 44,583 Transfer 18,304 13,617 — — 31,921 Customer solutions — — — 31,119 31,119 Recycling — 2,394 19,757 — 22,151 Organics — — — 26,847 26,847 Transportation — 9,383 — 1,504 10,887 Landfill gas-to-energy 798 2,296 — — 3,094 Total revenues $ 98,094 $ 135,783 $ 19,757 $ 59,470 $ 313,104 Transferred at a point-in-time $ 372 $ 614 $ 12,875 $ 2,082 $ 15,943 Transferred over time 97,722 135,169 6,882 57,388 297,161 Total revenues $ 98,094 $ 135,783 $ 19,757 $ 59,470 $ 313,104 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 $1,109 and $2,447 in the three and six months ended June 30, 2019 , respectively, and $1,616 and $3,084 in the three and six months ended June 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 six months ended June 30, 2019 and June 30, 2018 from performance obligations satisfied in previous periods. Contract receivables, which are included in Accounts receivable - trade, 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 - trade, net includes gross receivables from contracts of $83,942 and $73,500 as of June 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 $2,644 and $3,074 as of June 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 six months ended June 30, 2019 and June 30, 2018

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS In the six months ended June 30, 2019 , we acquired three tuck-in solid waste collection businesses in our Eastern region and a business comprised of solid waste collection, transfer and recycling operations in our Western region. In the six months ended June 30, 2018 , we acquired one solid waste collection, transfer and processing business in our Eastern region and one solid waste collection business 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: Six Months Ended 2019 2018 Purchase Price: Cash used in acquisitions, net of cash acquired $ 25,546 $ 19,189 Notes payable 2,250 — Contingent consideration and holdbacks 1,120 172 Total 28,916 19,361 Allocated as follows: Current assets 1,865 1,640 Land 726 — Buildings 2,602 5,578 Equipment 8,655 4,642 Intangible assets 11,619 2,700 Other liabilities, net (1,546 ) (1,276 ) Deferred tax liability (2,137 ) (1,635 ) Fair value of assets acquired and liabilities assumed 21,784 11,649 Excess purchase price allocated to goodwill $ 7,132 $ 7,712 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 Six Months Ended 2019 2018 2019 2018 Revenues $ 189,970 $ 183,084 $ 358,243 $ 348,373 Operating income $ 15,638 $ 16,606 $ 20,326 $ 18,919 Net income (loss) $ 11,954 $ 2,504 $ 10,357 $ (597 ) Basic earnings per share attributable to common stockholders: Weighted average common shares outstanding 47,464 42,661 46,693 42,516 Basic earnings per common share $ 0.25 $ 0.06 $ 0.22 $ (0.01 ) Diluted earnings per share attributable to common stockholders: Weighted average shares outstanding 48,221 43,916 47,424 42,516 Diluted earnings per common share $ 0.25 $ 0.06 $ 0.22 $ (0.01 ) 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

LEASES	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
LEASES	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. We amortize the consideration allocated to airspace rights as airspace is utilized on a units-of-consumption basis and such amortization is charged to cost of operations as airspace is consumed (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 Six Months Ended Lease cost: Amortization of right-of-use assets $ 503 $ 912 Interest expense 186 342 Fixed lease cost 4,317 8,544 Short-term lease cost 1,092 1,750 Variable lease cost 35 42 Total lease cost $ 6,133 $ 11,590 Other information: Cash paid for amounts included in the measurement of lease liabilities: Financing cash flows for finance leases $ 733 $ 1,204 Operating cash flows for operating leases $ 4,831 $ 6,874 Right-of-use assets obtained in exchange for new finance lease liabilities $ 4,384 $ 6,857 Right-of-use assets obtained in exchange for new operating lease liabilities $ 173 $ 588 June 30, Weighted-average remaining lease term - finance leases (years) 6.8 Weighted-average remaining lease term - operating leases (years) 11.3 Weighted-average discount rate - finance leases 5.2 % Weighted-average discount rate - operating leases 6.5 % Estimated minimum future lease obligations are as follows: Operating Leases Finance Leases Fiscal year ending December 31, 2019 $ 7,429 $ 1,670 Fiscal year ending December 31, 2020 12,878 3,872 Fiscal year ending December 31, 2021 10,470 3,336 Fiscal year ending December 31, 2022 8,324 2,740 Fiscal year ending December 31, 2023 6,558 2,572 Thereafter 65,739 6,924 Total lease payments 111,398 21,114 Less: interest expense (36,762 ) (3,946 ) Lease liability balance $ 74,636 $ 17,168
LEASES	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. We amortize the consideration allocated to airspace rights as airspace is utilized on a units-of-consumption basis and such amortization is charged to cost of operations as airspace is consumed (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 Six Months Ended Lease cost: Amortization of right-of-use assets $ 503 $ 912 Interest expense 186 342 Fixed lease cost 4,317 8,544 Short-term lease cost 1,092 1,750 Variable lease cost 35 42 Total lease cost $ 6,133 $ 11,590 Other information: Cash paid for amounts included in the measurement of lease liabilities: Financing cash flows for finance leases $ 733 $ 1,204 Operating cash flows for operating leases $ 4,831 $ 6,874 Right-of-use assets obtained in exchange for new finance lease liabilities $ 4,384 $ 6,857 Right-of-use assets obtained in exchange for new operating lease liabilities $ 173 $ 588 June 30, Weighted-average remaining lease term - finance leases (years) 6.8 Weighted-average remaining lease term - operating leases (years) 11.3 Weighted-average discount rate - finance leases 5.2 % Weighted-average discount rate - operating leases 6.5 % Estimated minimum future lease obligations are as follows: Operating Leases Finance Leases Fiscal year ending December 31, 2019 $ 7,429 $ 1,670 Fiscal year ending December 31, 2020 12,878 3,872 Fiscal year ending December 31, 2021 10,470 3,336 Fiscal year ending December 31, 2022 8,324 2,740 Fiscal year ending December 31, 2023 6,558 2,572 Thereafter 65,739 6,924 Total lease payments 111,398 21,114 Less: interest expense (36,762 ) (3,946 ) Lease liability balance $ 74,636 $ 17,168

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS A summary of the activity and balances related to goodwill by reporting segment is as follows: December 31, 2018 Acquisitions June 30, 2019 Eastern region $ 28,154 $ 2,566 $ 30,720 Western region 120,536 4,566 125,102 Recycling 12,315 — 12,315 Other 1,729 — 1,729 Total $ 162,734 $ 7,132 $ 169,866 A summary of intangible assets by intangible asset type follows: Covenants Not-to-Compete Client Lists Total Balance, June 30, 2019 Intangible assets $ 25,669 $ 52,063 $ 77,732 Less accumulated amortization (18,195 ) (16,190 ) (34,385 ) $ 7,474 $ 35,873 $ 43,347 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 $1,639 and $3,039 during the three and six months ended June 30, 2019 , respectively, as compared to $567 and $1,134 during the three and six months ended June 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 June 30, 2019 Fiscal year ending December 31, 2019 $ 3,443 Fiscal year ending December 31, 2020 $ 6,340 Fiscal year ending December 31, 2021 $ 5,417 Fiscal year ending December 31, 2022 $ 4,853 Fiscal year ending December 31, 2023 $ 4,565 Thereafter $ 18,729

ACCRUED FINAL CAPPING, CLOSURE

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	6 Months Ended
	Jun. 30, 2019
Asset Retirement Obligation Disclosure [Abstract]
ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	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: Six Months Ended 2019 2018 Beginning balance $ 73,075 $ 62,290 Obligations incurred 1,217 1,793 Revision in estimates (1) — 1,492 Accretion expense 3,194 2,784 Obligations settled (2) (2,947 ) (614 ) Ending balance $ 74,539 $ 67,745 (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

LONG-TERM DEBT	6 Months Ended
	Jun. 30, 2019
Debt And Derivatives Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT A summary of long-term debt and finance leases by debt instrument follows: June 30, December 31, Senior Secured Credit Facility: Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.75% $ 3,100 $ 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 2019; bearing interest at 4.00% 11,000 11,000 Other: Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2% 17,168 11,248 Notes payable maturing through June 2027; bearing interest at a weighted average of 3.4% 4,473 2,401 Principal amount of long-term debt and finance leases 496,741 555,249 Less—unamortized discount and debt issuance costs (1) 9,801 10,950 Long-term debt and finance leases less unamortized discount and debt issuance costs 486,940 544,299 Less—current maturities of long-term debt and finance leases 3,048 2,298 $ 483,892 $ 542,001 (1) A summary of unamortized discount and debt issuance costs by debt instrument follows: June 30, December 31, Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility") $ 6,298 $ 7,118 New York Bonds 2014 754 847 New York Bonds 2014R-2 420 450 FAME Bonds 2005R-3 475 517 FAME Bonds 2015R-1 587 622 FAME Bonds 2015R-2 455 493 Vermont Bonds 568 595 New Hampshire Bonds 244 308 $ 9,801 $ 10,950 Credit Facility As of June 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 2.25 x. 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 June 30, 2019 , further advances were available under the Credit Facility in the amount of $172,279 . 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 June 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 three and six months ended June 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 ("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 June 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 June 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 June 30, December 31, Interest rate swaps Other current assets $ 6 $ 338 Interest rate swaps Other non-current assets — 482 $ 6 $ 820 Interest rate swaps Other accrued liabilities $ 1,308 $ 387 Interest rate swaps Other long-term liabilities 4,152 1,555 $ 5,460 $ 1,942 Interest rate swaps Accumulated other comprehensive loss $ (5,712 ) $ (1,196 ) Interest rate swaps - tax provision Accumulated other comprehensive loss (112 ) (112 ) $ (5,824 ) $ (1,308 ) A summary of the amount of loss on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income into earnings follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Statement of Operations Location (Expense) Income (Expense) Income Interest expense $ (44 ) $ (38 ) $ (69 ) $ (91 )

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	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 is operated by SRD. 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: Six Months Ended 2019 2018 Beginning balance $ 5,173 $ 5,936 Accretion expense 65 78 Obligations settled (1) (392 ) (441 ) Ending balance $ 4,846 $ 5,573 (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: Six Months Ended 2019 2018 Beginning balance $ 5,614 $ 5,758 Obligations settled (1,764 ) (11 ) Ending balance $ 3,850 $ 5,747 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 to hear such cases. Our motion for a stay was granted in the New Hampshire Litigation. We intend to continue to vigorously defend against the New Hampshire Litigation, which we believe is without merit.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY Recent Developments In the six months ended June 30, 2019 , we completed a public offering 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. 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 June 30, 2019 , there were 1,398 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 (378 ) $ 6.03 Forfeited — $ — Outstanding, June 30, 2019 291 $ 6.80 5.4 $ 9,557 Exercisable, June 30, 2019 291 $ 6.80 5.4 $ 9,557 Stock-based compensation expense for stock options was $0 and $0 during the three and six months ended June 30, 2019 , respectively, as compared to $126 and $250 during the three and six months ended June 30, 2018 , respectively. During the three and six months ended June 30, 2019 , the aggregate intrinsic value of stock options exercised was $9,717 and $11,734 , 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 161 $ 37.02 Class A Common Stock Vested (216 ) $ 12.13 Forfeited (4 ) $ 17.75 Outstanding, June 30, 2019 627 $ 18.68 1.0 $ 10,854 Unvested, June 30, 2019 952 $ 19.48 1.1 $ 16,909 (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 $1,835 and $3,225 during the three and six months ended June 30, 2019 , respectively, as compared to $1,946 and $3,876 during the three and six months ended June 30, 2018 , respectively. During the three and six months ended June 30, 2019 , the total fair value of other stock awards vested was $831 and $7,721 , respectively. As of June 30, 2019 , total unrecognized stock-based compensation expense related to outstanding restricted stock and restricted stock units was $4,600 , which will be recognized over a weighted average period of 1.6 years . As of June 30, 2019 , maximum unrecognized stock-based compensation expense related to outstanding performance stock units, assuming the attainment of maximum performance targets, was $7,096 to be recognized over a weighted average period of 1.1 years . We also recorded $54 and $95 of stock-based compensation expense related to our Amended and Restated 1997 Employee Stock Purchase Plan during the three and six months ended June 30, 2019 , respectively, as compared to $48 and $71 during the three and six months ended June 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 (4,585 ) Amounts reclassified from accumulated other comprehensive loss 69 Income tax benefit (provision) related to items of other comprehensive loss — Net current-period other comprehensive loss (4,516 ) Balance, June 30, 2019 $ (5,824 ) A summary of reclassifications out of accumulated other comprehensive loss , net of tax follows: Three Months Ended Six Months Ended 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 $ 44 $ 38 $ 69 $ 91 Interest expense 44 38 69 91 Income (loss) before income taxes — — — — (Benefit) provision for income taxes $ 44 $ 38 $ 69 $ 91 Net income (loss)

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per share is computed by dividing the net income (loss) 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 Six Months Ended 2019 2018 2019 2018 Numerator: Net income (loss) $ 11,915 $ 1,704 $ 10,201 $ (2,206 ) Denominators: Number of shares outstanding, end of period: Class A common stock 46,599 41,765 46,599 41,765 Class B common stock 988 988 988 988 Shares to be issued - acquisition 36 — 36 — Unvested restricted stock (9 ) (38 ) (9 ) (38 ) Effect of weighted average shares outstanding (150 ) (54 ) (921 ) (199 ) Basic weighted average common shares outstanding 47,464 42,661 46,693 42,516 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards 757 1,255 731 — Diluted weighted average common shares outstanding 48,221 43,916 47,424 42,516 Anti-dilutive potentially issuable shares — — 154 2,105

OTHER ITEMS AND CHARGES

OTHER ITEMS AND CHARGES	6 Months Ended
	Jun. 30, 2019
Environmental Remediation Obligations [Abstract]
OTHER ITEMS AND CHARGES	OTHER ITEMS AND CHARGES Expense from Acquisition Activities and Other Items In the three and six months ended June 30, 2019 , we recorded charges of $464 and $1,140 , respectively, associated with acquisition activities. In the three and six months ended June 30, 2018 , we recorded charges of $211 and $211 , respectively, associated with the write-off of deferred costs related to the expiration of our shelf registration statement and $138 and $138 , respectively, associated with acquisition activities. Southbridge Landfill Closure Charge, Net In June 2017, we initiated the plan to cease operations of the Southbridge Landfill as disclosed in Note 9, Commitments and Contingencies. Accordingly, in the three and six months ended June 30, 2019 and 2018 , we recorded charges associated with the closure of the Southbridge Landfill as follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Charlton settlement charge (1) $ — $ — $ — $ 1,216 Legal and other costs (2) 917 172 1,472 543 Southbridge Landfill closure charge, net $ 917 $ 172 $ 1,472 $ 1,759 (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. Contract Settlement Charge In the six months ended June 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 six months ended June 30, 2018 , we recorded a development project charge of $311

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	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-trade, 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 - trade 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 June 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 $ 1,395 $ — $ — Interest rate swaps — 6 — $ 1,395 $ 6 $ — Liabilities: Interest rate swaps $ — $ 5,460 $ — 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 June 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 $128,734 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 June 30, 2019 , the carrying value of our Term Loan Facility was $350,000 and the carrying value of our Revolving Credit Facility was $3,100 . Their fair values are based on current borrowing rates for similar types of borrowing arrangements, or Level 2 inputs, and approximate their carrying values.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES During the three months ended June 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.

SEGMENT REPORTING

SEGMENT REPORTING	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
SEGMENT REPORTING	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 June 30, 2019 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 57,076 $ 14,678 $ 6,368 $ 4,227 $ 211,891 Western 85,356 24,213 11,419 10,338 530,756 Recycling 10,514 2,363 978 (214 ) 54,964 Other 34,513 660 950 1,193 68,349 Eliminations — (41,914 ) — — — $ 187,459 $ — $ 19,715 $ 15,544 $ 865,960 Three Months Ended June 30, 2018 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 53,589 $ 14,569 $ 7,030 $ 4,266 $ 180,330 Western 71,043 20,689 8,351 11,989 354,284 Recycling 9,600 1,738 1,043 (2,250 ) 49,477 Other 31,417 602 962 1,144 68,483 Eliminations — (37,598 ) — — — $ 165,649 $ — $ 17,386 $ 15,149 $ 652,574 Six Months Ended June 30, 2019 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 104,073 $ 25,449 $ 11,629 $ 3,600 $ 211,891 Western 158,989 44,314 21,659 15,696 530,756 Recycling 21,280 4,334 1,947 (1,155 ) 54,964 Other 66,781 1,193 1,969 1,845 68,349 Eliminations — (75,290 ) — — — Total $ 351,123 $ — $ 37,204 $ 19,986 $ 865,960 Six Months Ended June 30, 2018 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 98,094 $ 25,876 $ 13,009 $ 2,454 $ 180,330 Western 135,783 39,320 16,382 19,182 354,284 Recycling 19,757 2,923 2,097 (7,418 ) 49,477 Other 59,470 919 1,882 1,768 68,483 Eliminations — (69,038 ) — — — Total $ 313,104 $ — $ 33,370 $ 15,986 $ 652,574 A summary of our revenues attributable to services provided follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Collection $ 92,066 $ 74,564 $ 175,145 $ 141,039 Disposal 48,139 47,246 84,194 87,480 Power generation 711 1,295 1,847 3,094 Processing 1,908 2,347 2,786 3,768 Solid waste operations 142,824 125,452 263,972 235,381 Organics 14,905 14,647 28,501 26,847 Customer solutions 19,216 15,950 37,370 31,119 Recycling 10,514 9,600 21,280 19,757 Total revenues $ 187,459 $ 165,649 $ 351,123 $ 313,104

ACCOUNTING CHANGES (Policies)

ACCOUNTING CHANGES (Policies)	6 Months Ended
	Jun. 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 six months ended June 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 June 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 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 ) 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	Payments to customers that are not in exchange for a distinct good or service are recorded as a reduction of revenues. Contract receivables, which are included in Accounts receivable - trade, 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 - trade, net includes gross receivables from contracts of $83,942 and $73,500 as of June 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 $2,644 and $3,074 as of June 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 six months ended June 30, 2019 and June 30, 2018 , respectively, when the services were performed.
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. We amortize the consideration allocated to airspace rights as airspace is utilized on a units-of-consumption basis and such amortization is charged to cost of operations as airspace is consumed (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.
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.
Commitments and Contingencies	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.
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-trade, 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 - trade 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.
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.

ACCOUNTING CHANGES (Tables)

ACCOUNTING CHANGES (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Changes and Error Corrections [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	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 (Tables)

REVENUE RECOGNITION (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
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 six months ended June 30, 2019 and 2018 follows: Three Months Ended June 30, 2019 Eastern Western Recycling Other Total Revenues Collection $ 38,955 $ 54,151 $ — $ — $ 93,106 Landfill 5,427 18,855 — — 24,282 Transfer 11,923 8,597 — — 20,520 Customer solutions — — — 19,216 19,216 Recycling 577 341 10,514 — 11,432 Organics — — — 14,905 14,905 Transportation — 2,895 — 392 3,287 Landfill gas-to-energy 194 517 — — 711 Total revenues $ 57,076 $ 85,356 $ 10,514 $ 34,513 $ 187,459 Transferred at a point-in-time $ 52 $ 178 $ 5,051 $ 1,454 $ 6,735 Transferred over time 57,024 85,178 5,463 33,059 180,724 Total revenues $ 57,076 $ 85,356 $ 10,514 $ 34,513 $ 187,459 Three Months Ended June 30, 2018 Eastern Western Recycling Other Total Revenues Collection $ 34,625 $ 40,869 $ — $ — $ 75,494 Landfill 7,883 16,200 — — 24,083 Transfer 10,745 8,011 — — 18,756 Customer solutions — — — 15,950 15,950 Recycling — 1,445 9,600 — 11,045 Organics — — — 14,647 14,647 Transportation — 3,559 — 820 4,379 Landfill gas-to-energy 336 959 — — 1,295 Total revenues $ 53,589 $ 71,043 $ 9,600 $ 31,417 $ 165,649 Transferred at a point-in-time $ 181 $ 246 $ 5,618 $ 1,725 $ 7,770 Transferred over time 53,408 70,797 3,982 29,692 157,879 Total revenues $ 53,589 $ 71,043 $ 9,600 $ 31,417 $ 165,649 Six Months Ended June 30, 2019 Eastern Western Recycling Other Total Revenues Collection $ 72,919 $ 103,746 $ — $ — $ 176,665 Landfill 9,144 34,323 — — 43,467 Transfer 20,909 13,872 — — 34,781 Customer solutions — — — 37,370 37,370 Recycling 578 782 21,280 — 22,640 Organics — — — 28,501 28,501 Transportation — 4,942 — 910 5,852 Landfill gas-to-energy 523 1,324 — — 1,847 Total revenues $ 104,073 $ 158,989 $ 21,280 $ 66,781 $ 351,123 Transferred at a point-in-time $ 88 $ 487 $ 11,175 $ 1,721 $ 13,471 Transferred over time 103,985 158,502 10,105 65,060 337,652 Total revenues $ 104,073 $ 158,989 $ 21,280 $ 66,781 $ 351,123

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	6 Months Ended
	Jun. 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: Six Months Ended 2019 2018 Purchase Price: Cash used in acquisitions, net of cash acquired $ 25,546 $ 19,189 Notes payable 2,250 — Contingent consideration and holdbacks 1,120 172 Total 28,916 19,361 Allocated as follows: Current assets 1,865 1,640 Land 726 — Buildings 2,602 5,578 Equipment 8,655 4,642 Intangible assets 11,619 2,700 Other liabilities, net (1,546 ) (1,276 ) Deferred tax liability (2,137 ) (1,635 ) Fair value of assets acquired and liabilities assumed 21,784 11,649 Excess purchase price allocated to goodwill $ 7,132 $ 7,712
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 Six Months Ended 2019 2018 2019 2018 Revenues $ 189,970 $ 183,084 $ 358,243 $ 348,373 Operating income $ 15,638 $ 16,606 $ 20,326 $ 18,919 Net income (loss) $ 11,954 $ 2,504 $ 10,357 $ (597 ) Basic earnings per share attributable to common stockholders: Weighted average common shares outstanding 47,464 42,661 46,693 42,516 Basic earnings per common share $ 0.25 $ 0.06 $ 0.22 $ (0.01 ) Diluted earnings per share attributable to common stockholders: Weighted average shares outstanding 48,221 43,916 47,424 42,516 Diluted earnings per common share $ 0.25 $ 0.06 $ 0.22 $ (0.01 )

LEASES (Tables)

LEASES (Tables)	6 Months Ended
	Jun. 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 Six Months Ended Lease cost: Amortization of right-of-use assets $ 503 $ 912 Interest expense 186 342 Fixed lease cost 4,317 8,544 Short-term lease cost 1,092 1,750 Variable lease cost 35 42 Total lease cost $ 6,133 $ 11,590 Other information: Cash paid for amounts included in the measurement of lease liabilities: Financing cash flows for finance leases $ 733 $ 1,204 Operating cash flows for operating leases $ 4,831 $ 6,874 Right-of-use assets obtained in exchange for new finance lease liabilities $ 4,384 $ 6,857 Right-of-use assets obtained in exchange for new operating lease liabilities $ 173 $ 588 June 30, Weighted-average remaining lease term - finance leases (years) 6.8 Weighted-average remaining lease term - operating leases (years) 11.3 Weighted-average discount rate - finance leases 5.2 % Weighted-average discount rate - operating leases 6.5 %
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 $ 7,429 $ 1,670 Fiscal year ending December 31, 2020 12,878 3,872 Fiscal year ending December 31, 2021 10,470 3,336 Fiscal year ending December 31, 2022 8,324 2,740 Fiscal year ending December 31, 2023 6,558 2,572 Thereafter 65,739 6,924 Total lease payments 111,398 21,114 Less: interest expense (36,762 ) (3,946 ) Lease liability balance $ 74,636 $ 17,168
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 $ 7,429 $ 1,670 Fiscal year ending December 31, 2020 12,878 3,872 Fiscal year ending December 31, 2021 10,470 3,336 Fiscal year ending December 31, 2022 8,324 2,740 Fiscal year ending December 31, 2023 6,558 2,572 Thereafter 65,739 6,924 Total lease payments 111,398 21,114 Less: interest expense (36,762 ) (3,946 ) Lease liability balance $ 74,636 $ 17,168

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 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 June 30, 2019 Eastern region $ 28,154 $ 2,566 $ 30,720 Western region 120,536 4,566 125,102 Recycling 12,315 — 12,315 Other 1,729 — 1,729 Total $ 162,734 $ 7,132 $ 169,866
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, June 30, 2019 Intangible assets $ 25,669 $ 52,063 $ 77,732 Less accumulated amortization (18,195 ) (16,190 ) (34,385 ) $ 7,474 $ 35,873 $ 43,347 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 June 30, 2019 Fiscal year ending December 31, 2019 $ 3,443 Fiscal year ending December 31, 2020 $ 6,340 Fiscal year ending December 31, 2021 $ 5,417 Fiscal year ending December 31, 2022 $ 4,853 Fiscal year ending December 31, 2023 $ 4,565 Thereafter $ 18,729

ACCRUED FINAL CAPPING, CLOSUR_2

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE (Tables)	6 Months Ended
	Jun. 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: Six Months Ended 2019 2018 Beginning balance $ 73,075 $ 62,290 Obligations incurred 1,217 1,793 Revision in estimates (1) — 1,492 Accretion expense 3,194 2,784 Obligations settled (2) (2,947 ) (614 ) Ending balance $ 74,539 $ 67,745 (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 (Tables)

LONG-TERM DEBT (Tables)	6 Months Ended
	Jun. 30, 2019
Debt And Derivatives Disclosure [Abstract]
Summary of Components of Long-Term Debt and Capital Leases by Debt Instrument	A summary of long-term debt and finance leases by debt instrument follows: June 30, December 31, Senior Secured Credit Facility: Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.75% $ 3,100 $ 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 2019; bearing interest at 4.00% 11,000 11,000 Other: Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2% 17,168 11,248 Notes payable maturing through June 2027; bearing interest at a weighted average of 3.4% 4,473 2,401 Principal amount of long-term debt and finance leases 496,741 555,249 Less—unamortized discount and debt issuance costs (1) 9,801 10,950 Long-term debt and finance leases less unamortized discount and debt issuance costs 486,940 544,299 Less—current maturities of long-term debt and finance leases 3,048 2,298 $ 483,892 $ 542,001 (1) A summary of unamortized discount and debt issuance costs by debt instrument follows: June 30, December 31, Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility") $ 6,298 $ 7,118 New York Bonds 2014 754 847 New York Bonds 2014R-2 420 450 FAME Bonds 2005R-3 475 517 FAME Bonds 2015R-1 587 622 FAME Bonds 2015R-2 455 493 Vermont Bonds 568 595 New Hampshire Bonds 244 308 $ 9,801 $ 10,950
Schedule of Cash Flow Hedges Related to Derivative Instruments	A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows: Fair Value Balance Sheet Location June 30, December 31, Interest rate swaps Other current assets $ 6 $ 338 Interest rate swaps Other non-current assets — 482 $ 6 $ 820 Interest rate swaps Other accrued liabilities $ 1,308 $ 387 Interest rate swaps Other long-term liabilities 4,152 1,555 $ 5,460 $ 1,942 Interest rate swaps Accumulated other comprehensive loss $ (5,712 ) $ (1,196 ) Interest rate swaps - tax provision Accumulated other comprehensive loss (112 ) (112 ) $ (5,824 ) $ (1,308 )
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income	A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows: Fair Value Balance Sheet Location June 30, December 31, Interest rate swaps Other current assets $ 6 $ 338 Interest rate swaps Other non-current assets — 482 $ 6 $ 820 Interest rate swaps Other accrued liabilities $ 1,308 $ 387 Interest rate swaps Other long-term liabilities 4,152 1,555 $ 5,460 $ 1,942 Interest rate swaps Accumulated other comprehensive loss $ (5,712 ) $ (1,196 ) Interest rate swaps - tax provision Accumulated other comprehensive loss (112 ) (112 ) $ (5,824 ) $ (1,308 ) A summary of the amount of loss on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income into earnings follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Statement of Operations Location (Expense) Income (Expense) Income Interest expense $ (44 ) $ (38 ) $ (69 ) $ (91 ) 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 (4,585 ) Amounts reclassified from accumulated other comprehensive loss 69 Income tax benefit (provision) related to items of other comprehensive loss — Net current-period other comprehensive loss (4,516 ) Balance, June 30, 2019 $ (5,824 )

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Summary of Environmental Liability Associated with Potsdam	The changes to the environmental remediation liability associated with the Southbridge Landfill are as follows: Six Months Ended 2019 2018 Beginning balance $ 5,173 $ 5,936 Accretion expense 65 78 Obligations settled (1) (392 ) (441 ) Ending balance $ 4,846 $ 5,573 (1) Includes amounts that are being processed through accounts payable as a part of our disbursements cycle. A summary of the changes to the environmental remediation liability associated with the Potsdam environmental remediation liability follows: Six Months Ended 2019 2018 Beginning balance $ 5,614 $ 5,758 Obligations settled (1,764 ) (11 ) Ending balance $ 3,850 $ 5,747

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	6 Months Ended
	Jun. 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 (378 ) $ 6.03 Forfeited — $ — Outstanding, June 30, 2019 291 $ 6.80 5.4 $ 9,557 Exercisable, June 30, 2019 291 $ 6.80 5.4 $ 9,557
Summary of Restricted Stock, Restricted Stock Unit and Performance-based 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 161 $ 37.02 Class A Common Stock Vested (216 ) $ 12.13 Forfeited (4 ) $ 17.75 Outstanding, June 30, 2019 627 $ 18.68 1.0 $ 10,854 Unvested, June 30, 2019 952 $ 19.48 1.1 $ 16,909 (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.
Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Loss	A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows: Fair Value Balance Sheet Location June 30, December 31, Interest rate swaps Other current assets $ 6 $ 338 Interest rate swaps Other non-current assets — 482 $ 6 $ 820 Interest rate swaps Other accrued liabilities $ 1,308 $ 387 Interest rate swaps Other long-term liabilities 4,152 1,555 $ 5,460 $ 1,942 Interest rate swaps Accumulated other comprehensive loss $ (5,712 ) $ (1,196 ) Interest rate swaps - tax provision Accumulated other comprehensive loss (112 ) (112 ) $ (5,824 ) $ (1,308 ) A summary of the amount of loss on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income into earnings follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Statement of Operations Location (Expense) Income (Expense) Income Interest expense $ (44 ) $ (38 ) $ (69 ) $ (91 ) 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 (4,585 ) Amounts reclassified from accumulated other comprehensive loss 69 Income tax benefit (provision) related to items of other comprehensive loss — Net current-period other comprehensive loss (4,516 ) Balance, June 30, 2019 $ (5,824 )
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 Six Months Ended 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 $ 44 $ 38 $ 69 $ 91 Interest expense 44 38 69 91 Income (loss) before income taxes — — — — (Benefit) provision for income taxes $ 44 $ 38 $ 69 $ 91 Net income (loss)

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 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 Six Months Ended 2019 2018 2019 2018 Numerator: Net income (loss) $ 11,915 $ 1,704 $ 10,201 $ (2,206 ) Denominators: Number of shares outstanding, end of period: Class A common stock 46,599 41,765 46,599 41,765 Class B common stock 988 988 988 988 Shares to be issued - acquisition 36 — 36 — Unvested restricted stock (9 ) (38 ) (9 ) (38 ) Effect of weighted average shares outstanding (150 ) (54 ) (921 ) (199 ) Basic weighted average common shares outstanding 47,464 42,661 46,693 42,516 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards 757 1,255 731 — Diluted weighted average common shares outstanding 48,221 43,916 47,424 42,516 Anti-dilutive potentially issuable shares — — 154 2,105

OTHER ITEMS AND CHARGES (Tables

OTHER ITEMS AND CHARGES (Tables)	6 Months Ended
	Jun. 30, 2019
Environmental Remediation Obligations [Abstract]
Environmental Exit Costs by Cost	In June 2017, we initiated the plan to cease operations of the Southbridge Landfill as disclosed in Note 9, Commitments and Contingencies. Accordingly, in the three and six months ended June 30, 2019 and 2018 , we recorded charges associated with the closure of the Southbridge Landfill as follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Charlton settlement charge (1) $ — $ — $ — $ 1,216 Legal and other costs (2) 917 172 1,472 543 Southbridge Landfill closure charge, net $ 917 $ 172 $ 1,472 $ 1,759 (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.

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities 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 June 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 $ 1,395 $ — $ — Interest rate swaps — 6 — $ 1,395 $ 6 $ — Liabilities: Interest rate swaps $ — $ 5,460 $ — 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)

SEGMENT REPORTING (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Summary of Financial Information by Reportable Segment	Three Months Ended June 30, 2019 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 57,076 $ 14,678 $ 6,368 $ 4,227 $ 211,891 Western 85,356 24,213 11,419 10,338 530,756 Recycling 10,514 2,363 978 (214 ) 54,964 Other 34,513 660 950 1,193 68,349 Eliminations — (41,914 ) — — — $ 187,459 $ — $ 19,715 $ 15,544 $ 865,960 Three Months Ended June 30, 2018 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 53,589 $ 14,569 $ 7,030 $ 4,266 $ 180,330 Western 71,043 20,689 8,351 11,989 354,284 Recycling 9,600 1,738 1,043 (2,250 ) 49,477 Other 31,417 602 962 1,144 68,483 Eliminations — (37,598 ) — — — $ 165,649 $ — $ 17,386 $ 15,149 $ 652,574 Six Months Ended June 30, 2019 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 104,073 $ 25,449 $ 11,629 $ 3,600 $ 211,891 Western 158,989 44,314 21,659 15,696 530,756 Recycling 21,280 4,334 1,947 (1,155 ) 54,964 Other 66,781 1,193 1,969 1,845 68,349 Eliminations — (75,290 ) — — — Total $ 351,123 $ — $ 37,204 $ 19,986 $ 865,960 Six Months Ended June 30, 2018 Segment Outside revenues Inter-company revenues Depreciation and amortization Operating income (loss) Total assets Eastern $ 98,094 $ 25,876 $ 13,009 $ 2,454 $ 180,330 Western 135,783 39,320 16,382 19,182 354,284 Recycling 19,757 2,923 2,097 (7,418 ) 49,477 Other 59,470 919 1,882 1,768 68,483 Eliminations — (69,038 ) — — — Total $ 313,104 $ — $ 33,370 $ 15,986 $ 652,574
Summary of Revenues Attributable to Services Provided by Company	A summary of our revenues attributable to services provided follows: Three Months Ended Six Months Ended 2019 2018 2019 2018 Collection $ 92,066 $ 74,564 $ 175,145 $ 141,039 Disposal 48,139 47,246 84,194 87,480 Power generation 711 1,295 1,847 3,094 Processing 1,908 2,347 2,786 3,768 Solid waste operations 142,824 125,452 263,972 235,381 Organics 14,905 14,647 28,501 26,847 Customer solutions 19,216 15,950 37,370 31,119 Recycling 10,514 9,600 21,280 19,757 Total revenues $ 187,459 $ 165,649 $ 351,123 $ 313,104

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details)	6 Months Ended
	Jun. 30, 2019regional_operating_segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of regional operating segments	2

REVENUE RECOGNITION - Disaggreg

REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 187,459	$ 165,649	$ 351,123	$ 313,104
Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,735	7,770	13,471	15,943
Transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	180,724	157,879	337,652	297,161
Collection
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	93,106	75,494	176,665	142,502
Landfill
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24,282	24,083	43,467	44,583
Transfer
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20,520	18,756	34,781	31,921
Customer solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	19,216	15,950	37,370	31,119
Recycling
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11,432	11,045	22,640	22,151
Organics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,905	14,647	28,501	26,847
Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,287	4,379	5,852	10,887
Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	711	1,295	1,847	3,094
Eastern
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	57,076	53,589	104,073	98,094
Eastern | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	52	181	88	372
Eastern | Transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	57,024	53,408	103,985	97,722
Eastern | Collection
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	38,955	34,625	72,919	65,149
Eastern | Landfill
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,427	7,883	9,144	13,843
Eastern | Transfer
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11,923	10,745	20,909	18,304
Eastern | Customer solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eastern | Recycling
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	577	0	578	0
Eastern | Organics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eastern | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eastern | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	194	336	523	798
Western
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85,356	71,043	158,989	135,783
Western | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	178	246	487	614
Western | Transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85,178	70,797	158,502	135,169
Western | Collection
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	54,151	40,869	103,746	77,353
Western | Landfill
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18,855	16,200	34,323	30,740
Western | Transfer
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8,597	8,011	13,872	13,617
Western | Customer solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Western | Recycling
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	341	1,445	782	2,394
Western | Organics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Western | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,895	3,559	4,942	9,383
Western | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	517	959	1,324	2,296
Recycling
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10,514	9,600	21,280	19,757
Recycling | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,051	5,618	11,175	12,875
Recycling | Transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,463	3,982	10,105	6,882
Recycling | Collection
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Recycling | Landfill
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Recycling | Transfer
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Recycling | Customer solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Recycling | Recycling
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10,514	9,600	21,280	19,757
Recycling | Organics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Recycling | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Recycling | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34,513	31,417	66,781	59,470
Other | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,454	1,725	1,721	2,082
Other | Transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33,059	29,692	65,060	57,388
Other | Collection
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other | Landfill
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other | Transfer
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other | Customer solutions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	19,216	15,950	37,370	31,119
Other | Recycling
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other | Organics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14,905	14,647	28,501	26,847
Other | Transportation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	392	820	910	1,504
Other | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0	$ 0

REVENUE RECOGNITION - Narrative

REVENUE RECOGNITION - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ (187,459,000)	$ (165,649,000)	$ (351,123,000)	$ (313,104,000)
Revenue recognized	0	0	0	0
Gross receivables from contracts	83,942,000		83,942,000		$ 73,500,000
Contract liabilities	2,644,000		2,644,000		$ 3,074,000
Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 1,109,000	$ 1,616,000	$ 2,447,000	$ 3,084,000

BUSINESS COMBINATIONS - Additio

BUSINESS COMBINATIONS - Additional Information (Details) - business	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
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 | Waste Collection, Transfer and Processing Business
Business Acquisition [Line Items]
Number of businesses acquired		1
Western | Solid Waste Collection, Transfer and Recycling Business
Business Acquisition [Line Items]
Number of businesses acquired	1
Western | Solid Waste Collection
Business Acquisition [Line Items]
Number of businesses acquired		1

BUSINESS COMBINATIONS - Summary

BUSINESS COMBINATIONS - Summary of Purchase Price Paid for Acquisitions (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Purchase Price:
Cash used in acquisitions, net of cash acquired	$ 27,687	$ 19,369
Allocated as follows:
Excess purchase price allocated to goodwill	169,866		$ 162,734
Waste Collection Acquisitions
Purchase Price:
Cash used in acquisitions, net of cash acquired	25,546	19,189
Notes payable	2,250	0
Contingent consideration and holdbacks	1,120	172
Total	28,916	19,361
Allocated as follows:
Current assets	1,865	1,640
Land	726	0
Buildings	2,602	5,578
Equipment	8,655	4,642
Intangible assets	11,619	2,700
Other liabilities, net	(1,546)	(1,276)
Deferred tax liability	(2,137)	(1,635)
Fair value of assets acquired and liabilities assumed	21,784	11,649
Excess purchase price allocated to goodwill	$ 7,132	$ 7,712

BUSINESS COMBINATIONS - Schedul

BUSINESS COMBINATIONS - Schedule of Unaudited Pro forma Combined Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Combinations [Abstract]
Revenues	$ 189,970	$ 183,084	$ 358,243	$ 348,373
Operating income	15,638	16,606	20,326	18,919
Net income (loss)	$ 11,954	$ 2,504	$ 10,357	$ (597)
Basic weighted average common share outstanding (in shares)	47,464	42,661	46,693	42,516
Basic earnings per common share attributable to common stockholders (in dollars per share)	$ 0.25	$ 0.06	$ 0.22	$ (0.01)
Diluted weighted average shares outstanding (in shares)	48,221	43,916	47,424	42,516
Diluted earnings per share attributable to common stockholders (in dollars per share)	$ 0.25	$ 0.06	$ 0.22	$ (0.01)

LEASES - Schedule of Lease Cost

LEASES - Schedule of Lease Costs and Other Lease Information (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Lease cost:
Amortization of right-of-use assets	$ 503	$ 912
Interest expense	186	342
Fixed lease cost	4,317	8,544
Short-term lease cost	1,092	1,750
Variable lease cost	35	42
Total lease cost	6,133	11,590
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows for finance leases	733	1,204
Operating cash flows for operating leases	4,831	6,874
Right-of-use assets obtained in exchange for new finance lease liabilities	4,384	6,857
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 173	$ 588
Weighted-average remaining lease term - finance leases (years)	6 years 9 months 18 days	6 years 9 months 18 days
Weighted-average remaining lease term - operating leases (years)	11 years 3 months 18 days	11 years 3 months 18 days
Weighted-average discount rate - finance leases	5.20%	5.20%
Weighted-average discount rate - operating leases	6.50%	6.50%

LEASES - Schedule of estimated

LEASES - Schedule of estimated minimum future finance lease obligations (Details) $ in Thousands	Jun. 30, 2019USD ($)
Operating Leases
Fiscal year ending December 31, 2019	$ 7,429
Fiscal year ending December 31, 2020	12,878
Fiscal year ending December 31, 2021	10,470
Fiscal year ending December 31, 2022	8,324
Fiscal year ending December 31, 2023	6,558
Thereafter	65,739
Total lease payments	111,398
Less: interest expense	(36,762)
Lease liability balance	74,636
Finance Leases
Fiscal year ending December 31, 2019	1,670
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	21,114
Less: interest expense	(3,946)
Lease liability balance	$ 17,168

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Summary of Goodwill Activity (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 162,734
Acquisitions	7,132
Goodwill, ending balance	169,866
Eastern
Goodwill [Roll Forward]
Goodwill, beginning balance	28,154
Acquisitions	2,566
Goodwill, ending balance	30,720
Western
Goodwill [Roll Forward]
Goodwill, beginning balance	120,536
Acquisitions	4,566
Goodwill, ending balance	125,102
Recycling
Goodwill [Roll Forward]
Goodwill, beginning balance	12,315
Acquisitions	0
Goodwill, ending balance	12,315
Other
Goodwill [Roll Forward]
Goodwill, beginning balance	1,729
Acquisitions	0
Goodwill, ending balance	$ 1,729

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets by Intangible Asset Type (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 77,732	$ 66,113
Less accumulated amortization	(34,385)	(31,346)
Intangible assets, net	43,347	34,767
Covenants Not-to-Compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets	25,669	21,750
Less accumulated amortization	(18,195)	(17,584)
Intangible assets, net	7,474	4,166
Client Lists
Finite-Lived Intangible Assets [Line Items]
Intangible assets	52,063	44,363
Less accumulated amortization	(16,190)	(13,762)
Intangible assets, net	$ 35,873	$ 30,601

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible amortization expenses	$ 1,639	$ 567	$ 3,039	$ 1,134

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Amortization Expense Estimated (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Fiscal year ending December 31, 2019	$ 3,443
Fiscal year ending December 31, 2020	6,340
Fiscal year ending December 31, 2021	5,417
Fiscal year ending December 31, 2022	4,853
Fiscal year ending December 31, 2023	4,565
Thereafter	$ 18,729

ACCRUED FINAL CAPPING, CLOSUR_3

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE - Summary of Changes to Accrued Capping, Closure and Post-Closure Liabilities (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 73,075	$ 62,290
Obligations incurred	1,217	1,793
Revision in estimates	0	1,492
Accretion expense	3,194	2,784
Obligations settled	(2,947)	(614)
Ending balance	$ 74,539	$ 67,745

LONG-TERM DEBT - Summary of Com

LONG-TERM DEBT - Summary of Components of Long-Term Debt and Capital Leases by Debt Instrument (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term debt and capital lease	$ 496,741	$ 555,249
Finance leases maturing through December 2107; bearing interest at a weighted average of 5.2%	17,168
Less—unamortized discount and debt issuance costs	9,801	10,950
Long-term debt and finance leases less unamortized discount and debt issuance costs	486,940	544,299
Less—current maturities of long-term debt and finance leases	3,048	2,298
Non current portion of long term debt and capital lease obligation	$ 483,892	542,001
Weighted-average interest rate - finance leases	5.20%
Revolving line of credit facility (Revolving Credit Facility) due May 2023; bearing interest at LIBOR plus 1.75%
Debt Instrument [Line Items]
Long-term debt and capital lease	$ 3,100	$ 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]
Long-term debt and capital lease	$ 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%
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]
Long-term debt and capital lease	$ 25,000	$ 25,000
Less—unamortized discount and debt issuance costs	$ 754	$ 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]
Long-term debt and capital lease	$ 15,000	$ 15,000
Less—unamortized discount and debt issuance costs	$ 420	$ 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]
Long-term debt and capital lease	$ 25,000	$ 25,000
Less—unamortized discount and debt issuance costs	$ 475	$ 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]
Long-term debt and capital lease	$ 15,000	$ 15,000
Less—unamortized discount and debt issuance costs	$ 587	$ 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]
Long-term debt and capital lease	$ 15,000	$ 15,000
Less—unamortized discount and debt issuance costs	$ 455	$ 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]
Long-term debt and capital lease	$ 16,000	$ 16,000
Less—unamortized discount and debt issuance costs	$ 568	$ 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 2019; bearing interest at 4.00%
Debt Instrument [Line Items]
Long-term debt and capital lease	$ 11,000	$ 11,000
Less—unamortized discount and debt issuance costs	$ 244	$ 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]
Long-term debt and capital lease		$ 11,248
Weighted average interest rate		5.20%
Notes payable maturing through June 2027; bearing interest at a weighted average of 3.4%
Debt Instrument [Line Items]
Long-term debt and capital lease	$ 4,473	$ 2,401
Weighted average interest rate	3.40%	3.40%
Revolving Credit Facility and Term Loan Facility (collectively, the Credit Facility)
Debt Instrument [Line Items]
Less—unamortized discount and debt issuance costs	$ 6,298	$ 7,118

LONG-TERM DEBT - Credit Facilit

LONG-TERM DEBT - Credit Facility (Detail)	3 Months Ended
	Jun. 30, 2019USD ($)
Line of Credit
Debt Instrument [Line Items]
Debt instrument, term	5 years
Net leverage ratio	2.25
Line of credit facility, remaining borrowing capacity	$ 172,279,000
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, amount	24,621,000
Credit Facility
Debt Instrument [Line Items]
Additional revolver capacity	$ 125,000,000

LONG-TERM DEBT - Loss On Exting

LONG-TERM DEBT - Loss On Extinguishment of Debt (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Debt And Derivatives Disclosure [Abstract]
Loss on debt extinguishment	$ 0	$ 7,352	$ 0	$ 7,352

LONG-TERM DEBT - Cash Flow Hedg

LONG-TERM DEBT - Cash Flow Hedges (Details) - Cash Flow Hedging - Interest Rate Derivative	Jun. 30, 2019USD ($)interest_rate_derviative
Debt Instrument [Line Items]
Interest rate derivatives entered into | interest_rate_derviative	9
Notional amount | $	$ 190,000,000
Weighted average percentage rate paid	2.54%

LONG-TERM DEBT - Schedule Of Ca

LONG-TERM DEBT - Schedule Of Cash Flow Hedges Related to Derivative Instruments On the Balance Sheet (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, assets	$ 6		$ 6		$ 820
Cash flow hedge derivatives, liabilities	5,460		5,460		1,942
Unrealized (loss) gain resulting from changes in fair value of derivative instruments	(2,965)	$ (145)	(4,519)	$ 640
Other current assets | Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, assets	6		6		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	1,308		1,308		387
Other long-term liabilities | Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, liabilities	$ 4,152		4,152		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			(5,712)		(1,196)
Accumulated other comprehensive loss, interest rate swaps - tax provision			(112)		(112)
Accumulated other comprehensive loss			$ (5,824)		$ (1,308)

LONG-TERM DEBT - Schedule of Lo

LONG-TERM DEBT - Schedule of Loss On Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ (44)	$ (38)	$ (69)	$ (91)
Designated as Hedging Instrument | Interest rate swaps | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ (44)	$ (38)	$ (69)	$ (91)

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Additional Information (Detail)	Apr. 28, 2017USD ($)	Jun. 30, 2019	Apr. 26, 2017USD ($)	Jan. 29, 2016	Apr. 30, 2011USD ($)	May 31, 2009USD ($)	Dec. 20, 2000a
Southbridge Landfill
Loss Contingencies [Line Items]
Risk free interest percentage rate		2.60%
Potsdam Environmental Remediation Liability
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]
Amount of costs	$ 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 System
Loss Contingencies [Line Items]
Estimate of possible loss			$ 10,000,000

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Southbridge Landfill Environmental Remediation Liability (Details) - Southbridge Landfill - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 5,173	$ 5,936
Accretion expense	65	78
Obligations settled	(392)	(441)
Ending balance	$ 4,846	$ 5,573

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES - Potsdam Environmental Remediation Liability (Detail) - Potsdam Environmental Remediation Liability - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 5,614	$ 5,758
Obligations settled	(1,764)	(11)
Ending balance	$ 3,850	$ 5,747

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2016
Stock Options
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	$ 0	$ 126	$ 0	$ 250
Aggregate intrinsic value of options exercised	9,717		11,734
Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	1,835	1,946	$ 3,225	3,876
Restricted Stock Awards | 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]
Total fair value of other stock awards vested	831		$ 7,721
Unrecognized stock-based compensation expense	4,600		4,600
Maximum | Performance-Based Stock Units
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	7,096		$ 7,096
Weighted Average | Restricted Stock and Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense, weighted average period			1 year 7 months 6 days
Weighted Average | Performance-Based Stock Units
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense, weighted average period			1 year 1 month 6 days
2016 Plan
Limited Partners' Capital Account [Line Items]
Options granted period			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	$ 54	$ 48	$ 95	$ 71
Class A Common Stock | 2016 Plan
Limited Partners' Capital Account [Line Items]
Common stock, authorized shares (in shares)					2,250,000
Number of shares available for future grant (in shares)	1,398,000		1,398,000
Class A Common Stock | 2006 Incentive Plan
Limited Partners' Capital Account [Line Items]
Common stock, additional authorized shares (in shares)					2,723,000
Public Stock Offering | Class A Common Stock
Limited Partners' Capital Account [Line Items]
Sale of stock, number of shares issued (in shares)			3,565,000
Sale of stock, price per share (in dollars per share)	$ 29.50		$ 29.50
Sale of stock, net proceeds			$ 100,446

STOCKHOLDERS' EQUITY - Summary

STOCKHOLDERS' EQUITY - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)$ / sharesshares
Stock Options
Beginning balance, outstanding (in shares) | shares	669
Granted (in shares) | shares	0
Exercised (in shares) | shares	(378)
Forfeited (in shares) | shares	0
Ending balance, outstanding (in shares) | shares	291
Exercisable at end of period (in shares) | shares	291
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	6.03
Forfeited (in dollars per share) | $ / shares	0
Ending balance, outstanding (in dollars per share) | $ / shares	6.80
Exercisable at end of period (in dollars per share) | $ / shares	$ 6.80
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term, Outstanding	5 years 4 months 24 days
Weighted Average Remaining Contractual Term, Exercisable	5 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding at end of period | $	$ 9,557
Aggregate Intrinsic Value, Exercisable at end of period | $	$ 9,557

STOCKHOLDERS' EQUITY - Summar_2

STOCKHOLDERS' EQUITY - Summary of Restricted Stock, Restricted Stock Unit and Performance-based Stock Unit Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)$ / sharesshares
Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding at beginning of period (in shares)	686
Granted (in shares)	161
Forfeited (in shares)	(4)
Outstanding at end of period (in shares)	627
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 15.56
Granted (in dollars per share) | $ / shares	37.02
Forfeited (in dollars per share) | $ / shares	17.75
Outstanding at end of period (in dollars per share) | $ / shares	$ 18.68
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term, Outstanding	1 year
Aggregate Intrinsic Value, Outstanding at end of period | $	$ 10,854
Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units | Class A Common Stock
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Class A Common Stock Vested (in shares)	(216)
Weighted Average Grant Date Fair Value
Class A Common Stock Vested (in dollars per share) | $ / shares	$ 12.13
Performance-Based Stock Units
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value
Performance-based stock units, percentage of attainment level	100.00%
Performance-Based Stock Units | Class A Common Stock
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value
Number of performance-based stock units (in shares)	325
Unvested | Restricted Stock, Restricted Stock Units, and Performance-Based Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding at end of period (in shares)	952
Weighted Average Grant Date Fair Value
Outstanding at end of period (in dollars per share) | $ / shares	$ 19.48
Weighted Average Remaining Contractual Term (in years) and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term, Outstanding	1 year 1 month 6 days
Aggregate Intrinsic Value, Outstanding at end of period | $	$ 16,909

STOCKHOLDERS' EQUITY - Summar_3

STOCKHOLDERS' EQUITY - Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ (15,832)
Ending balance	96,197
Interest Rate Swaps
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,308)
Other comprehensive income before reclassifications	(4,585)
Amounts reclassified from accumulated other comprehensive income	69
Income tax benefit (provision) related to items of other comprehensive loss	0
Other comprehensive income (loss), net of tax	(4,516)
Ending balance	$ (5,824)

STOCKHOLDERS' EQUITY - Summar_4

STOCKHOLDERS' EQUITY - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 6,155		$ 6,469		$ 12,615	$ 12,922
Income (loss) before income taxes	9,990		1,749		8,304	(3,749)
(Benefit) provision for income taxes	(1,925)		45		(1,897)	(1,543)
Net income (loss)	11,915	$ (1,714)	1,704	$ (3,910)	10,201	(2,206)
Interest rate swaps | Interest Rate Swaps | Amounts Reclassified Out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	44		38		69	91
Income (loss) before income taxes	44		38		69	91
(Benefit) provision for income taxes	0		0		0	0
Net income (loss)	$ 44		$ 38		$ 69	$ 91

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Numerator:
Net income (loss)	$ 11,915	$ 1,704	$ 10,201	$ (2,206)
Number of shares outstanding, end of period:
Shares to be issued - acquisition (in shares)	36	0	36	0
Unvested restricted stock (in shares)	(9)	(38)	(9)	(38)
Effect of weighted average shares outstanding (in shares)	(150)	(54)	(921)	(199)
Basic weighted average common share outstanding (in shares)	47,464	42,661	46,693	42,516
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards (in shares)	757	1,255	731	0
Diluted weighted average shares outstanding (in shares)	48,221	43,916	47,424	42,516
Antidilutive potentially issuable shares (in shares)	0	0	154	2,105
Class A Common Stock
Number of shares outstanding, end of period:
Common stock, outstanding shares (in shares)	46,599	41,765	46,599	41,765	41,944
Class B Common Stock
Number of shares outstanding, end of period:
Common stock, outstanding shares (in shares)	988	988	988	988	988

OTHER ITEMS AND CHARGES (Detail

OTHER ITEMS AND CHARGES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Environmental Remediation Obligations [Abstract]
Acquisition activities	$ 464	$ 138	$ 1,140	$ 138
Write-off Of deferred costs		211		211
Site Contingency [Line Items]
Southbridge Landfill closure charge, net	917	172	1,472	1,759
Contract settlement charge	0	0	0	2,100
Project development charge	0	0	0	311
Southbridge Landfill
Site Contingency [Line Items]
Charlton settlement charge	0	0	0	1,216
Legal settlement	917	172	1,472	543
Southbridge Landfill closure charge, net	$ 917	$ 172	$ 1,472	$ 1,759

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring Fair Value Measurements (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets:
Restricted investment securities - landfill closure	$ 1,395	$ 1,248
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate swaps	0	0
Total	1,395	1,248
Liabilities:
Interest rate swaps	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted investment securities - landfill closure
Assets:
Restricted investment securities - landfill closure	1,395	1,248
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate swaps	6	820
Total	6	820
Liabilities:
Interest rate swaps	5,460	1,942
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Restricted investment securities - landfill closure
Assets:
Restricted investment securities - landfill closure	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate swaps	0	0
Total	0	0
Liabilities:
Interest rate swaps	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Restricted investment securities - landfill closure
Assets:
Restricted investment securities - landfill closure	$ 0	$ 0

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS - Additional Information (Detail) $ in Thousands	Jun. 30, 2019USD ($)
Significant Other Observable Inputs (Level 2)
Debt Instrument [Line Items]
Carrying value of revolver debt	$ 3,100
Fair Value | Fixed Rate Bonds
Debt Instrument [Line Items]
Fair value of fixed rate debt	128,734
Carrying Value | Fixed Rate Bonds
Debt Instrument [Line Items]
Fair value of fixed rate debt	122,000
Carrying Value | Term Loan B Facility due October 2023; bore interest at LIBOR plus 2.50% | Secured Debt
Debt Instrument [Line Items]
Fair value of fixed rate debt	$ 350,000

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	May 31, 2019
Income Tax Disclosure [Abstract]
Deferred tax benefit	$ (2,137)	$ (1,565)	$ (725)
Deferred tax liabilities, goodwill				$ 2,137

SEGMENT REPORTING - Summary of

SEGMENT REPORTING - Summary of Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 187,459	$ 165,649	$ 351,123	$ 313,104
Depreciation and amortization	19,715	17,386	37,204	33,370
Operating income (loss)	15,544	15,149	19,986	15,986
Total assets	865,960		865,960		$ 732,410
Operating Segments
Segment Reporting Information [Line Items]
Revenues	187,459	165,649	351,123	313,104
Depreciation and amortization	19,715	17,386	37,204	33,370
Operating income (loss)	15,544	15,149	19,986	15,986
Total assets	865,960	652,574	865,960	652,574
Operating Segments | Eastern
Segment Reporting Information [Line Items]
Revenues	57,076	53,589	104,073	98,094
Depreciation and amortization	6,368	7,030	11,629	13,009
Operating income (loss)	4,227	4,266	3,600	2,454
Total assets	211,891	180,330	211,891	180,330
Operating Segments | Western
Segment Reporting Information [Line Items]
Revenues	85,356	71,043	158,989	135,783
Depreciation and amortization	11,419	8,351	21,659	16,382
Operating income (loss)	10,338	11,989	15,696	19,182
Total assets	530,756	354,284	530,756	354,284
Operating Segments | Recycling
Segment Reporting Information [Line Items]
Revenues	10,514	9,600	21,280	19,757
Depreciation and amortization	978	1,043	1,947	2,097
Operating income (loss)	(214)	(2,250)	(1,155)	(7,418)
Total assets	54,964	49,477	54,964	49,477
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues	34,513	31,417	66,781	59,470
Depreciation and amortization	950	962	1,969	1,882
Operating income (loss)	1,193	1,144	1,845	1,768
Total assets	68,349	68,483	68,349	68,483
Eliminations
Segment Reporting Information [Line Items]
Revenues	(41,914)	(37,598)	(75,290)	(69,038)
Eliminations | Eastern
Segment Reporting Information [Line Items]
Revenues	14,678	14,569	25,449	25,876
Eliminations | Western
Segment Reporting Information [Line Items]
Revenues	24,213	20,689	44,314	39,320
Eliminations | Recycling
Segment Reporting Information [Line Items]
Revenues	2,363	1,738	4,334	2,923
Eliminations | Other
Segment Reporting Information [Line Items]
Revenues	$ 660	$ 602	$ 1,193	$ 919

SEGMENT REPORTING - Summary o_2

SEGMENT REPORTING - Summary of Revenues Attributable to Services Provided by Company (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from External Customer [Line Items]
Revenues	$ 187,459	$ 165,649	$ 351,123	$ 313,104
Collection
Revenue from External Customer [Line Items]
Revenues	92,066	74,564	175,145	141,039
Disposal
Revenue from External Customer [Line Items]
Revenues	48,139	47,246	84,194	87,480
Power generation
Revenue from External Customer [Line Items]
Revenues	711	1,295	1,847	3,094
Processing
Revenue from External Customer [Line Items]
Revenues	1,908	2,347	2,786	3,768
Solid waste operations
Revenue from External Customer [Line Items]
Revenues	142,824	125,452	263,972	235,381
Organics
Revenue from External Customer [Line Items]
Revenues	14,905	14,647	28,501	26,847
Customer solutions
Revenue from External Customer [Line Items]
Revenues	19,216	15,950	37,370	31,119
Recycling
Revenue from External Customer [Line Items]
Revenues	$ 10,514	$ 9,600	$ 21,280	$ 19,757

Uncategorized Items - cwst-0630

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