Supplemental Oil and Gas Disclosures - Costs Incurred in Oil and Natural Gas Property Acquisition, Exploration and Development Activities (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental Oil and Gas Disclosures [Abstract]
Proved oil and gas properties	$ 752,454	$ 3,159	$ 3,356
Unproved oil and gas properties	837,419	34,098	15,197
Exploration costs	2,260	3,250	1,685
Development costs	890,267	1,074,441	618,737
Asset retirement costs	11,856	9,359	5,055
Total costs incurred	$ 2,494,256	$ 1,124,307	$ 644,030