Derivative Financial Instruments and Fair Value Measurements - Derivatives Recorded at Fair Value in Consolidated Balance Sheets (Detail) - Not designated as hedging instruments - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 6,946	$ 2,416
Derivative Liabilities	2,047	12
Current | Commodities contracts
Derivatives, Fair Value [Line Items]
Derivative Assets	6,945	2,416
Derivative Liabilities	2,037	12
Non-current | Commodities contracts
Derivatives, Fair Value [Line Items]
Derivative Assets	1	0
Derivative Liabilities	$ 10	$ 0