Supplementary Quarterly Financial Data (Unaudited) - Summary of Results of Operations from Non-Routine Items (Detail) - USD ($) $ in Thousands	3 Months Ended							12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Gain (loss) on sale of oil and gas properties		$ (1,036)	$ (24)	$ (212)	$ (13,196)	$ (1,647)	$ 740	$ (1,060)	$ (14,315)
Net gain on extinguishment of debt				(1,064)	100,540	56,196	33,380		189,052	$ 78,741
Impairments of unproved oil and gas properties					(76,391)		(7,753)		(84,144)	(68,900)
Impairments of proved oil and gas properties	$ (43,990)			$ (2,561)	$ (113)	$ (1,742)	$ (22,718)	$ (43,990)	$ (27,134)	$ (801,347)