Restructuring Charges (Summary of Restructuring Charges Related to Fayetteville Shale) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 16	$ 11	$ 39
Non-cash curtailment gain			4
Fayetteville Shale
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)		5	12
Office consolidation		6	4
Total restructuring charges	$ 0	11	16
Non-cash curtailment gain			4
Fayetteville Shale \| Exploration and Production
Restructuring Cost and Reserve [Line Items]
Total restructuring charges		$ 11	$ 16

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes, but is not limited to, one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and termination benefits associated with an ongoing benefit arrangement. Excludes expenses associated with special or contractual termination benefits, a discontinued operation or an asset retirement obligation.

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