Suspended Exploratory Well Costs - Suspended Exploratory Well Costs (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014 Project	Dec. 31, 2013 Project
Extractive Industries [Abstract]
Balance at beginning of period	$ 6,964	$ 57,360
Additions to capitalized exploratory well costs pending the determination of proved reserves	90,767	39,832
Reclassifications to wells, facilities and equipment based on determination of proved reserves	(15,735)	(84,840)
Capitalized exploratory well costs charged to expense	0	0
Divested wells		(5,388)
Balance at end of period	81,996	6,964
Less exploratory well costs that have been capitalized for a period of one year or less	(46,412)
Capitalized exploratory well costs that have been capitalized for a period greater than one year	$ 35,584	$ 6,964
Number of projects that have exploratory well costs that have been capitalized for a period greater than one year	5	1