Integration and Restructuring Costs (Restructuring Activities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Reserve [Roll Forward]
Liability at beginning of period	$ 92	$ 124	$ 170
Expense Incurred	28	12	22
Cash Paid	(28)	(43)	(68)
Other	1	(1)
Liability at end of period	93	92	124
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period	7	11
Expense Incurred	17	4
Cash Paid	(7)	(8)
Other	(2)	0
Liability at end of period	15	7	11
Future rent under non-cancelable leases and other costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period	85	113
Expense Incurred	11	8
Cash Paid	(21)	(35)
Other	3	(1)
Liability at end of period	$ 78	$ 85	$ 113