Restructuring Restructuring - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring, Percentage of Employees Effected	15.00%
Restructuring and other termination costs	$ 53	$ (14)	$ 39	$ 12
Allocated Share-based Compensation Expense	16	25	68	81
Performance Shares [Member]
Restructuring Cost and Reserve [Line Items]
Allocated Share-based Compensation Expense	(3)	(30)	(34)	(10)
Restructuring Charges [Member] | Performance Shares [Member]
Restructuring Cost and Reserve [Line Items]
Allocated Share-based Compensation Expense	(1)	$ (17)	$ (16)	(11)
One-time Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other termination costs	$ 55
Spinoff [Member] | Seven Seven Energy Inc. [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other termination costs				$ 15