Reduction In Workforce (Summary Of Restructuring Charges) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 2	$ 77
Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	2	74
Midstream Services [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges		3
Workforce Reduction [Member]
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)		44
Stock-based compensation		24
Pension and other postretirement benefits	2	5
Other benefits		3
Outplacement services, other		1
Total restructuring charges	2	77
Workforce Reduction [Member] | Executive Management [Member]
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)		1
Stock-based compensation		3
Workforce Reduction [Member] | Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges	$ 2	74
Workforce Reduction [Member] | Midstream Services [Member]
Restructuring Cost and Reserve [Line Items]
Total restructuring charges		$ 3