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, 2019	Dec. 31, 2018
Summary of the changes in outstanding stock options
Outstanding, beginning of period (in shares)	2,125
Granted (in shares)	334
Exercised (in shares)	(286)
Forfeited (in shares)	(46)
Outstanding, end of period (in shares)	2,127	2,125
Options exercisable, ending of period (in shares)	1,492
Vested and expected, end of period (in shares)	2,067
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)	$ 43.08
Granted (in usd per share)	74.08
Exercised (in usd per share)	35.71
Forfeited (in usd per share)	67.04
Outstanding, end of period (in usd per share)	48.42	$ 43.08
Options exercisable, end of period (in usd per share)	39.60
Vested and expected, end of period (in usd per share)	$ 47.71
Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Roll Forward]
Outstanding, weighted average remaining contractual term	6 years 6 months	6 years 6 months
Aggregate intrinsic value, outstanding	$ 67
Options exercisable, end of period	5 years 6 months
Aggregate intrinsic value, exercisable	$ 60
Vested and expected to vest, end of period	6 years 4 months 24 days
Aggregate intrinsic value, vested and expected to vest	$ 66