Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Assets:
Restricted assets	$ 968	$ 6,632
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Restricted assets	968	6,632
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Restricted Assets - Capital Projects [Member]
Assets:
Restricted assets	142	5,819
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Restricted Assets - Landfill Closure [Member]
Assets:
Restricted assets	826	813
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities:
Interest rate derivative	$ 583	$ 1,668