Restructuring Charges (Details) - USD ($) $ in Millions	12 Months Ended			24 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 81	$ 26	$ 20
Payments for restructuring	45	8		$ 53
Severance costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	48	17
Payments for restructuring				35
Contract termination costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 33	$ 9
Payments for restructuring				$ 18