Accounting for Suspended Exploratory Wells (Details) $ in Millions		12 Months Ended
		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) Project	Dec. 31, 2014 USD ($) Project	Dec. 31, 2013 USD ($) Project
Changes in company's suspended exploratory well costs
Beginning balance at January 1		$ 4,195	$ 3,245	$ 2,681
Additions to capitalized exploratory well costs pending the determination of proved reserves		869	1,591	885
Reclassifications to wells, facilities and equipment based on the determination of proved reserves		(164)	(298)	(290)
Capitalized exploratory well costs charged to expense		(1,397)	(312)	(31)
Other reductions	[1]	(191)	(31)	0
Ending balance at December 31		3,312	4,195	3,245
Aging of capitalized well costs and number of project
Exploratory well costs capitalized for a period of one year or less					$ 489	$ 1,522	$ 641
Exploratory well costs capitalized for a period greater than one year					2,823	2,673	2,604
Balance at December 31		$ 4,195	$ 3,245	$ 2,681	$ 3,312	$ 4,195	$ 3,245
Number of projects with exploratory well costs that have been capitalized for a period greater than one year | Project	[2]				39	51	51

[1] Represents property sales.

[2] Certain projects have multiple wells or fields or both.