Property, Plant and Equipment - Capitalized Exploratory Well Costs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended						1 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Stampede [Member]	Sep. 30, 2013 Block WA-390-P, offshore Western Australia [Member]	Sep. 30, 2013 Pony Project - Block 468 [Member]	Sep. 30, 2013 Pony #3 Well - Block 469 [Member]	Sep. 30, 2013 Area 54, Offshore Libya [Member]	Feb. 28, 2013 Offshore Ghana [Member] Well
Significant Acquisitions and Disposals [Line Items]
Exploratory dry hole costs which were incurred and subsequently expensed	$ 80
Capitalized exploratory well costs greater than one year old after completion of drilling	$ 2,105
Capitalized well costs			40.00%	24.00%	7.00%	12.00%	12.00%
Working interest in the blocks		20.00%
Number of consecutive successful exploration wells							7