Fair Value Measurements - Financial Assets and Liabilities Valued on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative asset-current	$ 69	$ 388
Derivative asset-noncurrent	6	368
Derivative liability-current	(1,903)	(2,098)
Derivative liability-noncurrent	(1,028)	(1,673)
Derivative assets and liabilities, Total	(2,856)	(3,015)
Significant Other Observable Inputs (Level 2) [Member]
Derivatives, Fair Value [Line Items]
Derivative asset-current	69	388
Derivative asset-noncurrent	6	368
Derivative liability-current	(1,903)	(2,098)
Derivative liability-noncurrent	(1,028)	(1,673)
Derivative assets and liabilities, Total	$ (2,856)	$ (3,015)