Summary Of Significant Accounting Policies (Narrative) (Details)			3 Months Ended		12 Months Ended
		Jan. 01, 2019 USD ($)	Mar. 31, 2020	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($) Customer	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($) Customer
Summary Of Significant Accounting Policies [Line Items]
Settlement of long-term obligations duration					13 years
Number of customers | Customer					2	0	1
Derivative collateral held					$ 0
Cash collateral posted					0
Restricted cash					190,000,000	$ 380,000,000	$ 32,000,000
Right-of-use assets					223,000,000	243,000,000
Lease liabilities					255,000,000	261,000,000
Decrease in trading price of common stock			0.73
Foreign currency translation adjustment	[1]					$ 1,237,000,000
Canadian Business Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash					$ 170,000,000
Foreign currency translation adjustment				$ 1,200,000,000
ASU 2016-02 [Member] | Effect of Adoption of Lease Accounting [Member]
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets		$ 410,000,000
Lease liabilities		380,000,000
Cumulative effect on retained earnings, before tax		8,000,000
Cumulative effect on retained earnings		$ 7,000,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Other property and equipment, useful life					3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Other property and equipment, useful life					60 years
Customer Concentration Risk [Member] | One Customer [Member] | Consolidated Sales Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage					13.00%	10.00%	11.00%
Customer Concentration Risk [Member] | Two Customer [Member] | Consolidated Sales Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage					10.00%
Upstream Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days allowed for payment from end of production month					30 days
Marketing Revenues [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days allowed for payment of invoiced amount					30 days
Canadian Natural Resources Limited [Member] | Canadian Business Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Foreign currency translation adjustment						$ 1,200,000,000
CDM [Member] | QL Capital Partners, LP [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash distribution received					$ 14,000,000	100,000,000
Future capital commitments						40,000,000
Capital Increase Commitment Received					37,000,000,000
Cash contributed to entities					$ 21,000,000	$ 116,000,000,000

[1] In conjunction with the sale of substantially all of its oil and gas assets and operations in Canada, Devon released the cumulative translation adjustment as part of its gain on the disposition of its Canadian business. See Note 19 for additional details.