Restructuring Charges (Summary of Restructuring Charges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Stock-based compensation	$ 14	$ 24	$ 29
Total restructuring charges	39		73
Non-cash curtailment gain (loss)	4		(5)
Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	37
Midstream Services [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	2		3
Workforce Reduction [Member]
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)	21		44
Stock-based compensation			24
Other benefits			3
Outplacement services, other	2		2
Total restructuring charges	23		73
Workforce Reduction [Member] | Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	21		70
Workforce Reduction [Member] | Midstream Services [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	2		3
Fayetteville Shale [Member]
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)	12
Office consolidation	4
Total restructuring charges	16
Fayetteville Shale [Member] | Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 16