Derivative Instruments - Realized and Unrealized Gains and Losses on Derivative Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on derivatives, net			$ 68,420	$ (114,972)
Gain (loss) on crude oil and natural gas derivatives, net	$ 28,022	$ (82,257)	74,880	(40,145)
Diesel Fuel [Member]
Cash received (paid) on derivatives:
Cash received (paid) on derivatives, net	185	0	919	0
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on derivatives, net	(1,098)	4,200	(3,729)	3,140
Gain (loss) on crude oil and natural gas derivatives, net	(913)	4,200	(2,810)	3,140
Swap [Member] | Natural Gas [Member]
Cash received (paid) on derivatives:
Cash received (paid) on derivatives, net	6,709	38,778	12,187	77,967
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on derivatives, net	12,520	(101,308)	35,416	(98,915)
Collars | Natural Gas [Member]
Cash received (paid) on derivatives:
Cash received (paid) on derivatives, net	(3,050)	0	(9,456)	0
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on derivatives, net	11,843	(19,733)	36,733	(19,235)
Call Option [Member] | Crude Oil [Member]
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on derivatives, net	0	6	0	38
Crude Oil and Natural Gas [Member]
Cash received (paid) on derivatives:
Cash received (paid) on derivatives, net	3,659	38,778	2,731	77,967
Non-cash gain (loss) on derivatives:
Non-cash gain (loss) on derivatives, net	24,363	(121,035)	72,149	(118,112)
Gain (loss) on crude oil and natural gas derivatives, net	$ 28,022	$ (82,257)	$ 74,880	$ (40,145)