Divestitures (Narrative) (Details) $ in Millions, $ in Billions	1 Months Ended	3 Months Ended			12 Months Ended
	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($) MMBoe	Dec. 31, 2019 USD ($)	Dec. 31, 2019 CAD ($)
Business Acquisition [Line Items]
Gain recognized on sale of business, pre tax				$ (1)
Asset impairment charges		$ 179
Gain on asset dispositions				45
Non Core Assets [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment				300
Gain on asset dispositions				$ 45
Total estimated proved reserves | MMBoe				25
Barnett Shale [Member]
Business Acquisition [Line Items]
Asset impairment charges		$ 179	$ 748
Canadian Natural Resources Limited [Member] | Canadian Business Segment [Member]
Business Acquisition [Line Items]
Proceeds from sale of business					$ 2,600	$ 3.4
Effective close date of divestiture		Jun. 27, 2019
Gain recognized on sale of business, pre tax					223
Gain recognized on sale of business, net of tax					$ 425
BKV [Member] | Barnett Shale [Member] | Scenario Forecast [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment	$ 570