Suspended Exploratory Well Costs (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Capitalized Exploratory Well Costs [Abstract]
Suspended exploratory well costs	$ 1,500,000,000	$ 2,200,000,000
Exploratory well costs previously capitalized as suspended exploratory well costs for greater than one year at December 31, 2013, charged to dry hole expense	$ 0
Rovuma Offshore Area 1 in Mozambique [Member] | Oil and Gas Exploration and Production Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Working interest sold	10.00%