Segment Disclosures and Related Information - Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 2,749	$ 7,953	$ 8,907	$ 17,103
Natural Gas [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,190	1,915	2,845	4,918
Natural Gas Liquids Reserves [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	84	213	235	451
Crude Oil [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,216	4,813	4,660	9,394
Other Products [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	259	1,012	1,167	2,340
U.S.
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,844	5,225	6,061	10,911
Australia
Segment Reporting Information [Line Items]
Sales and other operating revenues	168	311	605	870
Canada
Segment Reporting Information [Line Items]
Sales and other operating revenues	165	382	498	955
China
Segment Reporting Information [Line Items]
Sales and other operating revenues	67	159	213	402
Indonesia
Segment Reporting Information [Line Items]
Sales and other operating revenues	132	226	336	431
Libya
Segment Reporting Information [Line Items]
Sales and other operating revenues	0	267	44	521
Malaysia
Segment Reporting Information [Line Items]
Sales and other operating revenues	83	334	299	670
Norway
Segment Reporting Information [Line Items]
Sales and other operating revenues	242	561	688	1,149
United Kingdom
Segment Reporting Information [Line Items]
Sales and other operating revenues	46	485	156	1,189
Other foreign Countries
Segment Reporting Information [Line Items]
Sales and other operating revenues	2	3	7	5
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	2,749	7,953	8,907	17,103
Alaska [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	419	1,426	1,532	2,833
Alaska [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	438	1,426	1,551	2,833
Alaska [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	19	0	19	0
Lower 48 [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,433	3,809	4,536	7,962
Lower 48 [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,405	3,798	4,498	7,939
Lower 48 [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	(28)	(11)	(38)	(23)
Canada
Segment Reporting Information [Line Items]
Sales and other operating revenues	165	717	678	1,540
Canada \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	165	382	498	955
Canada \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	0	(335)	(180)	(585)
Europe and North Africa [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	288	1,313	888	2,859
Asia Pacific and Middle East [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	450	1,030	1,453	2,373
Other International [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1	0	4	0
Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 2	$ 4	$ 15	$ 144