Summarized Quarterly Financial Information - Unaudited - Results of Operations by Quarter (Detail) - USD ($) $ / shares in Units, $ 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, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Operating revenue	$ 110,499	$ 132,196	$ 149,525	$ 153,498	$ 184,780	$ 183,213	$ 207,046	$ 223,830	$ 544,649	$ 795,542	$ 974,179
Loss from operations	(342,759)	(297,209)	(228,161)	(497,194)	(286,147)	(34,356)	16,613	48,552	(1,365,323)	(255,338)	241,981
Net income (loss)	$ (318,656)	$ (291,965)	$ (152,906)	$ (327,388)	$ (190,515)	$ (29,415)	$ 4,444	$ 25,943	$ (1,090,915)	$ (189,543)	$ 117,634
Basic earnings (loss) per share (in usd per share)	$ (5.76)	$ (5.28)	$ (2.77)	$ (5.93)	$ (3.47)	$ (0.54)	$ 0.08	$ 0.52	$ (19.75)	$ (3.60)	$ 2.36
Diluted earnings (loss) per share (in usd per share)	$ (5.76)	$ (5.28)	$ (2.77)	$ (5.93)	$ (3.47)	$ (0.54)	$ 0.08	$ 0.52	$ (19.75)	$ (3.60)	$ 2.36
Write-down of oil and gas properties before income tax effect	$ 351,062	$ 295,679	$ 224,294	$ 491,412	$ 304,062	$ 47,130	$ 0	$ 0	$ 1,362,447	$ 351,192	$ 0
Write-down of oil and gas properties net of income tax effect	$ 224,680	$ 189,235	$ 143,548	$ 314,504	$ 194,600	$ 30,163	$ 0	$ 0