Impairments (Before Tax Impairment Charges) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Impairments		$ 674	$ 813	$ 405
Alaska [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Impairments		5	0	0
Lower 48 [Member]
Segment Reporting Information [Line Items]
Impairments		(89)
Lower 48 [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Impairments	$ 84	(8)	804	402
Canada | Operating Segments [Member]
Segment Reporting Information [Line Items]
Impairments		6	3	2
Europe, Middle East and North Africa [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Impairments		(24)	6	1
Asia Pacific [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Impairments		$ 695	$ 0	$ 0