Crude Oil and Natural Gas Property Information - Schedule of Aggregate Capitalized Costs Relates to Crude Oil and Natural Gas Producing Activities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
Proved crude oil and natural gas properties	$ 12,423,878	$ 8,980,505
Unproved crude oil and natural gas properties	1,181,268	1,073,944
Total	13,605,146	10,054,449
Less accumulated depreciation, depletion and amortization	(3,083,180)	(2,090,845)
Net capitalized costs	$ 10,521,966	$ 7,963,604