Restructuring Charges (Summary of Restructuring Charges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Stock-based compensation	$ 8	$ 14	$ 24
Total restructuring charges	11	39	0
Non-cash curtailment gain (loss)		4
Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)		21
Stock-based compensation		0
Other benefits		0
Outplacement services, other		2
Total restructuring charges	0	23	0
Workforce Reduction | Exploration and Production
Restructuring Cost and Reserve [Line Items]
Total restructuring charges		21
Workforce Reduction | Marketing
Restructuring Cost and Reserve [Line Items]
Total restructuring charges		2
Fayetteville Shale
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)	5	12
Office consolidation	6	4
Total restructuring charges	11	16	$ 0
Non-cash curtailment gain (loss)		4
Fayetteville Shale | Exploration and Production
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 11	$ 16