Summarized Quarterly Financial Information - Unaudited - Results of Operations by Quarter (non-printing) (Detail) - USD ($) $ 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]
Write-down of oil and gas properties, before tax	$ 351,062	$ 295,679	$ 224,294	$ 491,412	$ 304,062	$ 47,130	$ 0	$ 0	$ 1,362,447	$ 351,192	$ 0
Franchise tax settlement									0	0	12,590
Loss on early extinguishment of debt, before tax									$ 0	$ 0	$ 27,279