Restructuring Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Separations
Restructuring charge and reserve
Restructuring charges		$ 24	$ 45
Restructuring reserve	$ 3	4
Facility Closings
Restructuring charge and reserve
Restructuring reserve	5	11
Benefit (loss) recognized as a result of lease modification	$ 0	3	1
Network Related Expenses [Member] | Employee Separations
Restructuring charge and reserve
Restructuring charges		8	11
General and Administrative Expense [Member] | Employee Separations
Restructuring charge and reserve
Restructuring charges		$ 16	$ 34