Estimated inflation rate.

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Summary Of Significant Accounting Policies [Line Items]

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Amount of surety bonds that are available for the future payment of landfill capping, closure and post-closure obligations.

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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Amount of interest capitalized during the period.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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Summary of Significant Accounting Policies - Landfill Development Cost- Additional Information (Detail) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Apr. 30, 2014	Apr. 30, 2013
Summary Of Significant Accounting Policies [Line Items]
Capitalized interest	$ 333	$ 62	$ 256	$ 368
Estimate of inflation rate		2.00%
Accretion expense	2,275	$ 3,370	3,967
Closure and Post-Closure Costs [Member]
Summary Of Significant Accounting Policies [Line Items]
Accretion expense	2,275	3,370	3,967	$ 3,538
Surety bond	144,633	156,163	133,847
Letters of credit	$ 1,104	$ 1,000	$ 1,104
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Rate of asset retirement obligation		9.10%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Rate of asset retirement obligation		9.50%