Derivative Instruments - Realized and Unrealized Gains and Losses on Derivative Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on crude oil and natural gas derivatives, net			$ (105,009)	$ 26,011
Gain (loss) on crude oil and natural gas derivatives, net	$ 15,668	$ 46,527	(24,477)	74,545
Diesel Fuel [Member]
Cash received on derivatives:
Cash received (paid) on derivatives, net	100
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on crude oil and natural gas derivatives, net	500		2,600
Swap [Member] | Natural Gas [Member]
Cash received on derivatives:
Cash received (paid) on derivatives, net	5,174	5,142	83,141	29,084
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on crude oil and natural gas derivatives, net	5,298	36,257	(93,617)	33,453
Collars | Natural Gas [Member]
Cash received on derivatives:
Cash received (paid) on derivatives, net	0	6,775	0	19,450
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on crude oil and natural gas derivatives, net	5,196	(2,264)	(14,039)	(11,986)
Call Option [Member] | Crude Oil [Member]
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on crude oil and natural gas derivatives, net	0	617	38	4,544
Crude Oil and Natural Gas [Member]
Cash received on derivatives:
Cash received (paid) on derivatives, net	5,174	11,917	83,141	48,534
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on crude oil and natural gas derivatives, net	10,494	34,610	(107,618)	26,011
Gain (loss) on crude oil and natural gas derivatives, net	$ 15,668	$ 46,527	$ (24,477)	$ 74,545