Reduction in Workforce (Summary of Restructuring Charges) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)	$ 44
Stock-based compensation	24
Pension and other postretirement benefits	5
Other benefits	3
Outplacement services, other	2
Total restructuring charges	78
Workforce Reduction [Member] | Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	75
Workforce Reduction [Member] | Midstream Services [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 3