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COMMITMENTS AND CONTINGENCIES - Additional Information (Detail) |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jul. 17, 2018 USD ($) | Apr. 28, 2017 USD ($) | Nov. 30, 2016 basin | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Jun. 30, 2016 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Dec. 31, 2018 USD ($) | Apr. 26, 2017 USD ($) | Jan. 29, 2016 | Apr. 30, 2011 USD ($) | May 31, 2009 USD ($) | Dec. 20, 2000 a
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of storm water basins | basin |  |  | 2 |  |  |  |  |  |  |  |  |  |  |
Litigation settlement, future cash payments |  |  |  |  |  |  | $ 850,000 |  |  |  |  |  |  |
Ancillary services, period |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |
Litigation settlement, total cash and services |  |  |  |  |  |  | $ 1,200,000 |  |  |  |  |  |  |
Litigation settlement, amount awarded form other party |  |  |  | $ 10,000,000 | $ 0 |  | 10,000,000 | $ 0 |  |  |  |  |  |
Litigation settlement received |  |  |  |  |  | $ 0 | $ 992,000 |  |  |  |  |  |  |
Southbridge Landfill |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk free interest percentage rate |  |  |  | 2.60% |  |  | 2.60% |  |  |  |  |  |  |
Reserve for probable loss |  |  |  | $ 366,000 |  |  | $ 366,000 |  |  |  |  |  |  |
Litigation settlement received |  |  |  |  |  |  | $ 3,506,000 | $ 0 |  |  |  |  |  |
Potsdam Environmental Remediation Liability |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk free interest percentage rate |  |  |  | 1.50% |  |  | 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% |  |  |
Maximum | Southbridge Landfill | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on contract termination |  |  |  |  |  |  |  |  | $ 2,199,000 |  |  |  |  |
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 |  |  |  |
Steadfast Insurance Company |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Litigation settlement, amount awarded form other party | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Litigation settlement received | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |

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