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Commitments and Contingencies - Additional Information (Detail) | 1 Months Ended | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Apr. 30, 2011 USD ($) | May 31, 2009 USD ($) | Jun. 30, 2016 USD ($) a | Dec. 31, 2015 USD ($) | Feb. 29, 2016 Resident | Jan. 29, 2016
Expera Old Town LLC [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Reserve related with settlement |  |  | $ 1,355,000 | $ 2,616,000 |  |
Contract settlement charge |  |  |  | 1,940,000 |  |
Reserve related with settlement |  |  |  | $ 676,000 |  |
Reserve for legal costs |  |  | 34,000 |  |  |
Expera Old Town LLC [Member] | Upon Execution of SA [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Litigation settlement |  |  | 1,250,000 |  |  |
Expera Old Town LLC [Member] | Five years following execution of SA [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Litigation settlement |  |  | 350,000 |  |  |
Southbridge Recycling and Disposal Park, Inc [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Number of resident's homes representing legal suit | Resident |  |  |  |  | 40 |
Maximum [Member] | Expera Old Town LLC [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Annual fuel replacement fee |  |  | $ 2,000,000 |  |  |
Contract maturity year |  |  | 2036 |  |  |
Minimum [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Investigative expenditure incurred, expect recovery amount |  |  | $ 1,548 |  |  |
Potsdam Environmental Remediation Liability [Member] |  |  |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |  |  |
Scrap yard and solid waste transfer station | a |  |  | 25 |  |  |
Estimate of total undiscounted costs associated with implementing the preferred remedies | $ 12,130,000 | $ 10,219,000 |  |  |  |
Remediation activities, participant share percentage |  |  |  |  |  | 15.00%
Risk free interest rate |  |  | 1.80% |  |  |

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