Supplemental Information on Oil and Gas Operations (Unaudited) (Narrative) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2020 USD ($) MMBoe $ / bbl $ / Mcf	Dec. 31, 2019 USD ($) MMBoe	Dec. 31, 2018 USD ($) MMBoe	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2017 USD ($) MMBoe
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves	[1]	752	757	823				787
Standardized measure of discounted future net cash flows | $		$ 3,472	$ 5,398	$ 7,150				$ 5,954
Proved developed and undeveloped reserves, revisions due to prices	[1]	(78)	(28)	15
Proved developed and undeveloped reserves, revisions other than price (MMBoe)		55	75
Proved developed and undeveloped reserves, additional downward revisions other than price(MMBoe)		20	5
Proved developed and undeveloped reserves, extensions and discoveries	[1]	135	160	206
Proved developed and undeveloped reserves, extensions and discoveries related to additions from infill drilling activities (MMBoe)				21
Proved undeveloped reserves increased percentage		6.00%
Proved undeveloped reserves as percentage of entire proved reserves		24.00%
Proved undeveloped reserves	[1]	178	168	223				202
Proved undeveloped reserves due to drilling and development activities (MMBoe)		105
Proved undeveloped reserves, conversion to proved developed reserves (MMBoe)		68
Proved undeveloped reserves to proved developed reserves conversion percentage		40.00%
Cost incurred related to development and conversion of proved undeveloped reserves | $		$ 448
Average estimated future realized price per barrel of oil used to estimate future cash inflows for proved oil reserves | $ / bbl		37.35
Average estimated future realized price per Mcf of gas used to estimate future cash inflows for proved gas reserves | $ / Mcf		1.37
Average estimated future realized price per barrel of natural gas liquids used to estimate future cash inflows for proved NGL reserves | $ / bbl		10.76
Future development costs | $		$ 1,747	$ 2,093	$ 2,957
Future dismantlement, abandonment and rehabilitation costs | $		$ 300
Scenario Forecast [Member]
Reserve Quantities [Line Items]
Future development costs | $					$ 200	$ 400	$ 600
Delaware Basin [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves, revisions other than price (MMBoe)		40	6
Proved developed and undeveloped reserves, extensions and discoveries		117	77	88
Percentage of extensions and discoveries proved undeveloped reserves		87.00%
Proved undeveloped reserves revisions other than price		8
STACK [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves, revisions other than price (MMBoe)		22	9
Proved developed and undeveloped reserves, extensions and discoveries		8	37	87
Eagle Ford [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves, extensions and discoveries		5	18
Powder River Basin [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves, extensions and discoveries		5	28
STACK and Delaware Basin [Member]
Reserve Quantities [Line Items]
Percentage of additions to proved developed and undeveloped reserves for extensions and discoveries				85.00%
Anadarko Basin
Reserve Quantities [Line Items]
Proved undeveloped reserves revisions other than price		12
Barnett Shale Discontinued Operations [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves			612
Standardized measure of discounted future net cash flows | $			$ 940
Discontinued Operations [Member]
Reserve Quantities [Line Items]
Proved developed and undeveloped reserves				1,104
Standardized measure of discounted future net cash flows | $				$ 3,042

[1] Gas reserves are converted to Boe at the rate of six Mcf per Bbl of oil, based upon the approximate relative energy content of gas and oil. NGL reserves are converted to Boe on a one-to-one basis with oil. The conversion rates are not necessarily indicative of the relationship of oil, natural gas and NGL prices.