Supplemental Information on Oil and Gas Producing Activities (Unaudited) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Capitalized Costs Relating to Oil and Gas Producing Activities
Proved properties	$ 8,211,106	$ 6,515,221
Unproved properties	1,996,081	2,060,936
Total	10,207,187	8,576,157
Accumulated depletion and depreciation	(1,415,005)	(802,665)
Net capitalized costs	8,792,182	7,773,492
Costs Incurred in Certain Oil and Gas Activities
Proved property		64,066	$ 15,300
Unproved property	198,694	777,422	440,825
Development costs	1,039,301	1,536,193	780,583
Exploration costs	611,981	940,957	835,382
Total costs incurred	1,849,976	3,318,638	2,072,090
Results of Operations for Oil and Gas Producing Activities
Revenues	1,375,128	1,736,752	821,445
Operating expenses:
Production expenses	773,697	578,672	278,348
Exploration expenses	3,846	27,893	22,272
Depletion and depreciation	614,700	418,744	219,830
Impairment of unproved properties	104,321	15,198	10,928
Results of operations before income tax expense (benefit)	(121,436)	696,245	290,067
Income tax expense	45,497	(263,126)	(110,805)
Results of operations	$ (75,939)	$ 433,119	$ 179,262