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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% |  |

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