Supplemental Information on Oil and Gas Producing Activities (Unaudited) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Capitalized Costs Relating to Oil and Gas Producing Activities
Proved properties	$ 9,549,671	$ 8,211,106
Unproved properties	2,331,173	1,996,081
Total	11,880,844	10,207,187
Accumulated depletion and depreciation	(2,089,500)	(1,415,005)
Net capitalized costs	9,791,344	8,792,182
Costs Incurred in Certain Oil and Gas Activities
Proved property	134,113		$ 64,066
Unproved property	611,631	198,694	777,422
Development costs	1,000,903	1,039,301	1,536,193
Exploration costs	326,856	611,981	940,957
Total costs incurred	2,073,503	1,849,976	3,318,638
Results of Operations for Oil and Gas Producing Activities
Revenues	1,755,061	1,375,128	1,736,752
Operating expenses:
Production expenses	999,516	773,697	578,672
Exploration expenses	6,862	3,846	27,893
Depletion and depreciation	700,274	614,700	418,744
Impairment of unproved properties	162,935	104,321	15,198
Results of operations before income tax expense (benefit)	(114,526)	(121,436)	696,245
Income tax expense	43,334	45,497	(263,126)
Results of operations	$ (71,192)	$ (75,939)	$ 433,119