DIVESTITURE TRANSACTIONS DIVESTITURE TRANSACTIONS (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Divestiture transactions	$ 0	$ 0	$ (5,517,000)
Remaining divestiture costs	19,251,000	14,916,000
Proceeds from sale of assets	0	$ 0	5,335,000
Disposal Group, Not Discontinued Operations | Casella-Altela Regional Environmental Services, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Membership interest				51.00%
Disposal Group, Not Discontinued Operations | Maine Energy Facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Undiscounted purchase consideration					$ 6,650,000
Undiscounted purchase consideration paid in installments					21 years
Divestiture transactions			1,149,000
Remaining divestiture costs	$ 0
Disposal Group, Not Discontinued Operations | Western
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received from sale of assets			872,000
Gain (loss) on disposal			590,000
Disposal Group, Not Discontinued Operations | Western | Cares
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge				$ 7,455,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Casella-Altela Regional Environmental Services, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal			2,850,000
Proceeds from sale of assets			3,500,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Casella-Altela Regional Environmental Services, LLC | Equipment and Real Estate
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal			928,000
Proceeds from sale of assets			$ 1,050,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Altela, Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Membership interest			49.00%