Fair Value Measurements - Financial Assets and Liabilities Valued on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative asset-current	$ 5	$ 69
Derivative asset-noncurrent	5	6
Derivative liability-current	(1,293)	(1,903)
Derivative liability-noncurrent	(464)	(1,028)
Derivative assets and liabilities, Total	(1,747)	(2,856)
Significant Other Observable Inputs (Level 2) [Member]
Derivatives, Fair Value [Line Items]
Derivative asset-current	5	69
Derivative asset-noncurrent	5	6
Derivative liability-current	(1,293)	(1,903)
Derivative liability-noncurrent	(464)	(1,028)
Derivative assets and liabilities, Total	$ (1,747)	$ (2,856)