Segments - Schedule of Industry Segments and Eliminations (Details) shares in Millions, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2021 USD ($) shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment shares	Sep. 30, 2020 USD ($)
Segment Information
Number of operating segments | segment				3
Net sales		$ 6,792	$ 4,108	$ 18,043	$ 13,649
Income (loss) from continuing operations before income taxes		1,217	(4,058)	1,675	(14,280)
Income tax benefit (expense)		(387)	403	(446)	1,896
Income (loss) from continuing operations		830	(3,655)	1,229	(12,384)
Gain (loss) on derivative instrument		(26)	88	150	(573)
Anadarko acquisition-related costs		29	5	122	302
Disposed of by Sale, Not Discontinued Operations | WES Midstream segment
Segment Information
Gain (loss) on sale	$ 102
Number of limited partner units sold (in units) | shares	11.5
Operating Segments | Oil and gas
Segment Information
Net sales		4,955	2,989	13,124	10,089
Income (loss) from continuing operations before income taxes		1,467	(1,072)	2,036	(8,570)
Income tax benefit (expense)		0	0	0	0
Income (loss) from continuing operations		1,467	(1,072)	2,036	(8,570)
Gain (loss) on derivative instrument		(97)		(277)	1,100
Impairment charge		17		173	7,000
Gain (loss) on sale			(795)		(795)
Operating Segments | Chemical
Segment Information
Net sales		1,396	937	3,671	2,745
Income (loss) from continuing operations before income taxes		407	178	970	472
Income tax benefit (expense)		0	0	0	0
Income (loss) from continuing operations		407	178	970	472
Operating Segments | Midstream and marketing
Segment Information
Net sales		702	364	2,006	1,358
Income (loss) from continuing operations before income taxes		20	(2,791)	272	(4,085)
Income tax benefit (expense)		0	0	0	0
Income (loss) from continuing operations		20	(2,791)	272	(4,085)
Gain (loss) on derivative instrument		(11)		(176)
Goodwill impairment			2,700		2,700
Goodwill written off			1,400
Operating Segments | Midstream and marketing | Disposed of by Sale, Not Discontinued Operations | WES Midstream segment
Segment Information
Gain (loss) on sale				$ 124
Number of limited partner units sold (in units) | shares				11.5
Corporate and Eliminations
Segment Information
Net sales		(261)	(182)	$ (758)	(543)
Income (loss) from continuing operations before income taxes		(677)	(373)	(1,603)	(2,097)
Income tax benefit (expense)		(387)	403	(446)	1,896
Income (loss) from continuing operations		(1,064)	30	(2,049)	$ (201)
Loss from debt tenders		88		88
Mark to market gain (loss) on interest rate swaps		(26)	(577)	150
Anadarko acquisition-related costs		$ 29	$ 302	$ 122