Impairments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Impairment charges by segment, before-tax
Asset Impairment Charges	$ 856	$ 529	$ 680
Exploration expenses	2,045	1,232	1,500
Alaska [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges	59	3	3
Lower 48 [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges	208	2	192
Exploration expenses	239
Canada [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges	38	216	262
Exploration expenses	145
Europe [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges	541	301	211
Asia Pacific and Middle East [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges	7	3	4
Corporate [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges	3	4	8
McKenzie Gas Project [Member]
Impairment charges by segment, before-tax
Asset Impairment Charges			213
Exploration expenses			$ 481