Share-based Compensation Plans Share-based Compensation Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
RSUs and PSUs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	37,778,224
Minimum Range for PSU Awards Payable Upon Vest	0.00%
Maximum range for PSU awards payable upon vest	150.00%
Restricted Stock Units and Performance Share Units	$ 60	$ 54	$ 49
Number of RSU and PSU shares [Member]
RSUs and PSUs [Line Items]
Outstanding RSUs and PSUs	5,443,000
Granted RSUs and PSUs	3,280,000
Vested RSUs and PSUs	(3,043,000)
Forfeited RSUs and PSUs	(88,000)
Outstanding RSUs and PSUs	5,592,000	5,443,000
Weighted-average grant date fair value per share [Member]
RSUs and PSUs [Line Items]
Outstanding RSUs and PSUs	19.00
Granted RSUs and PSUs	21.30
Vested RSUs and PSUs	19.84
Forfeited RSUs and PSUs	19.39
Outstanding RSUs and PSUs	19.89	19.00