Fair Value Measurements - Financial Assets and Liabilities Valued on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative asset - current	$ 578	$ 388
Derivative asset - noncurrent	852	368
Derivative liability - current	(2,361)	(2,098)
Derivative liability - noncurrent	(3,165)	(1,673)
Derivative assets and liabilities, Total	(4,096)	(3,015)
Significant Other Observable Inputs Level 2 Member
Derivatives, Fair Value [Line Items]
Derivative asset - current	578	388
Derivative asset - noncurrent	852	368
Derivative liability - current	(2,361)	(2,098)
Derivative liability - noncurrent	(3,165)	(1,673)
Derivative assets and liabilities, Total	$ (4,096)	$ (3,015)