Share-Based Compensation Plans (Summary of Stock Options Grant) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Summary of the changes in outstanding stock options
Outstanding, beginning of period (in shares)	2,561
Granted (in shares)	463
Exercised (in shares)	(797)
Forfeited (in shares)	(44)
Outstanding, end of period (in shares)	2,183	2,561
Options exercisable, ending of period (in shares)	1,222
Vested and expected, end of period (in shares)	2,098
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of period (in usd per share)	$ 31.16
Granted (in usd per share)	37.90
Exercised (in usd per share)	27.91
Forfeited (in usd per share)	35.55
Outstanding, end of period (in usd per share)	33.68	$ 31.16
Options exercisable, end of period (in usd per share)	29.40
Vested and expected, end of period (in usd per share)	$ 33.53
Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Roll Forward]
Outstanding, weighted average remaining contractual term	7 years 2 months 12 days	6 years 9 months 18 days
Aggregate intrinsic value of outstanding stock options	$ 41
Options exercisable, end of period	5 years 10 months 24 days
Aggregate intrinsic value of exercisable stock options	$ 26
Vested and expected to vest, end of period	7 years 1 month 6 days
Aggregate intrinsic value, vested and expected to vest	$ 40