Share-Based Compensation Plans (Summary of Stock Options Grant) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Summary of the changes in outstanding stock options
Outstanding, beginning of period (in shares)	2,040
Granted (in shares)	334
Exercised (in shares)	(130)
Forfeited (in shares)	(5)
Outstanding, end of period (in shares)	2,239	2,040
Options exercisable, ending of period (in shares)	1,615
Vested and expected, end of period (in shares)	2,146
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)	$ 48.56
Granted (in usd per share)	80.66
Exercised (in usd per share)	41.18
Forfeited (in usd per share)	74.37
Outstanding, end of period (in usd per share)	53.72	$ 48.56
Options exercisable, end of period (in usd per share)	44.45
Vested and expected, end of period (in usd per share)	$ 52.67
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 8 months 12 days	6 years 3 months 18 days
Aggregate intrinsic value, outstanding	$ 37
Options exercisable, end of period	5 years 8 months 12 days
Aggregate intrinsic value, exercisable	$ 36
Vested and expected to vest, end of period	6 years 6 months
Aggregate intrinsic value, vested and expected to vest	$ 36