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	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Asset, Fair Value	$ 6,946	$ 2,416
Liability, Fair Value	2,047	12
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	6,946	2,416
Liability, Fair Value	2,047	12
Level 3
Derivatives, Fair Value [Line Items]
Asset, Fair Value	0	0
Liability, Fair Value	$ 0	$ 0