Industry Segments - Schedule of Industry Segments and Eliminations (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)
Segment Information
Number of operating segments | segment			4
Net sales	$ 5,687	$ 5,216	$ 14,111	$ 13,062
Income (loss) from continuing operations before income taxes	(621)	2,579	1,176	4,776
Income tax expense	(116)	(710)	(647)	(1,351)
Income (loss) from continuing operations	(737)	1,869	529	3,425
Anadarko merger-related costs	924	0	974	0
Amortization of debt financing fees	65		122
Operating Segments | Oil and Gas
Segment Information
Net sales	3,821	2,889	8,890	7,874
Income (loss) from continuing operations before income taxes	221	767	1,431	2,297
Income tax expense	0	0	0	0
Income (loss) from continuing operations	221	767	1,431	2,297
Operating Segments | Chemical
Segment Information
Net sales	1,071	1,185	3,128	3,515
Income (loss) from continuing operations before income taxes	207	321	680	936
Income tax expense	0	0	0	0
Income (loss) from continuing operations	207	321	680	936
Operating Segments | Marketing and Other Midstream
Segment Information
Net sales	780	1,367	2,505	2,359
Income (loss) from continuing operations before income taxes	266	1,698	876	2,127
Income tax expense	0	0	0	0
Income (loss) from continuing operations	266	1,698	876	2,127
Operating Segments | WES Midstream
Segment Information
Net sales	383	0	383	0
Income (loss) from continuing operations before income taxes	134	0	134	0
Income tax expense	0	0
Income (loss) from continuing operations	134	0	134	0
Corporate and Eliminations
Segment Information
Net sales	(368)	(225)	(795)	(686)
Income (loss) from continuing operations before income taxes	(1,449)	(207)	(1,945)	(584)
Income tax expense	(116)	(710)	(647)	(1,351)
Income (loss) from continuing operations	$ (1,565)	$ (917)	$ (2,592)	$ (1,935)