Fair Value Measurements - Schedule of Fair Value Measured on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total fair value	$ (12,633)	$ 34,441
Commodity Contract [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total fair value	(12,633)	34,441
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total fair value	(12,633)	34,441
Level 2 [Member] | Commodity Contract [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total fair value	$ (12,633)	$ 34,441