Segment Disclosures and Related Information - Sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 4,386	$ 7,756	$ 13,293	$ 24,859
Natural Gas [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1,509	1,799	4,354	6,717
Natural Gas Liquids Reserves [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	129	156	364	607
Crude Oil [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	2,321	4,612	6,981	14,006
Other Products [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	427	1,189	1,594	3,529
U.S.
Segment Reporting Information [Line Items]
Sales and other operating revenues	3,148	5,085	9,209	15,996
Australia
Segment Reporting Information [Line Items]
Sales and other operating revenues	0	412	605	1,282
Canada
Segment Reporting Information [Line Items]
Sales and other operating revenues	328	360	826	1,315
China
Segment Reporting Information [Line Items]
Sales and other operating revenues	161	191	374	593
Indonesia
Segment Reporting Information [Line Items]
Sales and other operating revenues	167	223	503	654
Libya
Segment Reporting Information [Line Items]
Sales and other operating revenues	6	288	50	809
Malaysia
Segment Reporting Information [Line Items]
Sales and other operating revenues	148	258	447	928
Norway
Segment Reporting Information [Line Items]
Sales and other operating revenues	358	632	1,046	1,781
United Kingdom
Segment Reporting Information [Line Items]
Sales and other operating revenues	68	305	224	1,494
Other foreign Countries
Segment Reporting Information [Line Items]
Sales and other operating revenues	2	2	9	7
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	4,386	7,756	13,293	24,859
Alaska [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	864	1,296	2,396	4,129
Alaska [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	834	1,296	2,385	4,129
Alaska [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	(30)	0	(11)	0
Lower 48 [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	2,323	3,728	6,859	11,690
Lower 48 [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	2,314	3,718	6,812	11,657
Lower 48 [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	(9)	(10)	(47)	(33)
Canada
Segment Reporting Information [Line Items]
Sales and other operating revenues	348	633	1,026	2,173
Canada \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	328	360	826	1,315
Canada \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	(20)	(273)	(200)	(858)
Europe, Middle East and North Africa [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	432	1,225	1,320	4,084
Asia Pacific [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	477	1,085	1,930	3,458
Other International [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	1	0	5	0
Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Sales and other operating revenues	$ 0	$ 72	$ 15	$ 216