General (Details) - USD ($) shares in Millions, $ in Millions		1 Months Ended		3 Months Ended				9 Months Ended		12 Months Ended
	Dec. 30, 2019	Aug. 31, 2020	Apr. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018
Noncontrolling Interest [Line Items]
Anadarko acquisition-related costs				$ (5)			$ (924)	$ (302)	$ (974)
Impairment and related charges					$ 8,600
Income taxes paid								375	827
Domestic tax refunds				223					5
Interest paid				1,300					611
Cash and cash equivalents				1,896			4,840	1,896	4,840		$ 3,032
Restricted cash and restricted cash equivalents				51			467	51	467		485
Cash and restricted cash included in assets held for sale				113			3	113	3
Restricted cash and restricted cash equivalents included in long-term receivables and other assets, net				14			55	14	55
Cash, cash equivalents, restricted cash and restricted cash equivalents				2,074			5,365	2,074	5,365		3,574	$ 3,033
Equity method investment amounts				3,125				3,125			6,389
Loss from equity investment				(123)			$ (104)	(183)	(274)
Note payable retired								260	$ 0
WES
Noncontrolling Interest [Line Items]
Loss on non-cash transaction								46
Common units exchanged to retire note payable		27.9
Note payable retired		$ 260
Sales				46				165
WES | Purchases
Noncontrolling Interest [Line Items]
Purchases				164				474
WES | Transportation, gathering and other fees paid
Noncontrolling Interest [Line Items]
Purchases				258				$ 804
WES Midstream segment
Noncontrolling Interest [Line Items]
Non-voting general partner interest								2.00%
Limited partner interest								51.50%
Effective economic interest								53.50%
Ownership interest, intended reduction								50.00%
Pro-rata interest in net assets				370				$ 370
Public Ownership | WES Midstream segment | Variable Interest Entity, Primary Beneficiary
Noncontrolling Interest [Line Items]
Limited partner interest	44.60%
WES Midstream segment
Noncontrolling Interest [Line Items]
Equity method investment amounts				1,900				1,900			$ 5,100
Loss from equity investment						$ 440
Impairment of equity method investment				2,700
Algeria Africa Assets | Discontinued Operations, Disposed of by Sale
Noncontrolling Interest [Line Items]
Impairment and related charges			$ 931
Ghana Assets
Noncontrolling Interest [Line Items]
Impairment and related charges				$ 1,400				1,400
Ghana Assets | Discontinued Operations, Disposed of by Sale
Noncontrolling Interest [Line Items]
Impairment and related charges					$ 1,400
Anadarko
Noncontrolling Interest [Line Items]
Anadarko acquisition-related costs								(302)
Domestic tax refunds								$ 881		$ 881