Derivative Financial Instruments and Fair Value Measurements - Summary of Derivative Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Commodities Contracts - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Asset, Fair Value	$ 2,276	$ 317
Liability, Fair Value	5,431	10,713
Level 1
Derivatives, Fair Value [Line Items]
Asset, Fair Value	0	0
Liability, Fair Value	0	0
Level 2
Derivatives, Fair Value [Line Items]
Asset, Fair Value	2,276	317
Liability, Fair Value	5,431	10,713
Level 3
Derivatives, Fair Value [Line Items]
Asset, Fair Value	0	0
Liability, Fair Value	$ 0	$ 0