Supplemental Oil and Gas Disclosures (Unaudited) - Capitalized Costs (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Reserve Quantities [Line Items]
Proved properties	$ 42,693	$ 41,728	[1]
Unproved properties	1,969	2,277	[1]
Capitalized costs, gross	44,662	44,005
Accumulated DD&A	(26,972)	(24,457)
Capitalized costs, net	17,690	19,548
United States [Member]
Reserve Quantities [Line Items]
Proved properties	19,170	18,692
Unproved properties	1,465	1,615
Capitalized costs, gross	20,635	20,307
Accumulated DD&A	(10,034)	(9,027)
Capitalized costs, net	10,601	11,280
Canada [Member]
Reserve Quantities [Line Items]
Proved properties	5,434	5,812
Unproved properties	109	172
Capitalized costs, gross	5,543	5,984
Accumulated DD&A	(4,120)	(3,958)
Capitalized costs, net	1,423	2,026
Egypt [Member]
Reserve Quantities [Line Items]
Proved properties	10,169	9,798
Unproved properties	76	25
Capitalized costs, gross	10,245	9,823
Accumulated DD&A	(7,287)	(6,559)
Capitalized costs, net	2,958	3,264
North Sea [Member]
Reserve Quantities [Line Items]
Proved properties	7,920	7,426
Unproved properties	280	429
Capitalized costs, gross	8,200	7,855
Accumulated DD&A	(5,531)	(4,913)
Capitalized costs, net	2,669	2,942
Other International [Member]
Reserve Quantities [Line Items]
Proved properties	0	0
Unproved properties	39	36
Capitalized costs, gross	39	36
Accumulated DD&A	0	0
Capitalized costs, net	$ 39	$ 36

[1] Financial information for 2015 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.