Crude Oil and Natural Gas Property Information - Schedule of Capitalized Exploratory Drilling Costs Pending Evaluation (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Well	Dec. 31, 2014 USD ($) Well	Dec. 31, 2013 USD ($) Well
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	$ 1,700
Number Of Wells With Capitalized Exploratory Well Costs Suspended One Year Beyond Completion Of Drilling	3
Suspended Well Costs Incurred		$ 100	$ 1,600
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Balance at January 1	$ 93,421	152,775	92,699
Additions to capitalized exploratory well costs pending determination of proved reserves	132,806	627,853	548,933
Reclassification to proved crude oil and natural gas properties based on the determination of proved reserves	(160,779)	(671,618)	(479,507)
Capitalized exploratory well costs charged to expense	(6,051)	(15,589)	(9,350)
Balance at December 31	$ 59,397	$ 93,421	$ 152,775
Number of wells | Well	73	119	67