Derivative Instruments and Fair Value Measurements - Summary of Change in Fair Value of Commodity Derivatives (Detail) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Total gain (loss) on commodity derivatives	$ 14,552	$ 12,755	$ 9,281	$ 15,901	$ 7,782	$ (764)	$ (3,320)	$ (1,339)	$ 199	$ (840)	$ (714)	$ 307	$ 52,489	$ 2,359	$ (1,048)
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total gain (loss) on commodity derivatives													19,275	44,472	(5,644)
Derivatives Not Designated as Hedging Instruments [Member] \| Unrealized Gain (Loss) on Commodity Derivatives [Member]
Derivatives, Fair Value [Line Items]
Total gain (loss) on commodity derivatives													(33,214)	42,113	(4,596)
Derivatives Not Designated as Hedging Instruments [Member] \| Realized Gain (Loss) on Commodity Derivatives [Member]
Derivatives, Fair Value [Line Items]
Total gain (loss) on commodity derivatives													$ 52,489	$ 2,359	$ (1,048)