Share-Based Compensation Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Outstanding at beginning of period (in shares)	672	574	1,127
Granted (in shares)	174	122	145
Exercised (in shares)	(79)	(24)	(680)
Expired or cancelled (in shares)	(44)		(18)
Outstanding at end of period (in shares)	723	672	574
Vested or expected to vest (in shares)	722	670	571
Exercisable (in shares)	426	401	220
Wtd. Avg. Exercise Price Per Share
Outstanding at beginning of period (in dollars per share)	$ 85	$ 77	$ 66
Granted (in dollars per share)	84	123	97
Exercised (in dollars per share)	65	78	64
Expired or cancelled (in dollars per share)	91		75
Outstanding at end of period (in dollars per share)	87	85	77
Vested or expected to vest (in dollars per share)	87	85	77
Exercisable (in dollars per share)	$ 82	$ 76	$ 65
Wtd. Avg. Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding (in years)	6 years 1 month 6 days	5 years 10 months 24 days	7 years 1 month 6 days
Vested or expected to vest (in years)	6 years 1 month 6 days	5 years 10 months 24 days	7 years 1 month 6 days
Exercisable (in years)	4 years 6 months	4 years 6 months	5 years 3 months 18 days
Outstanding	$ 10	$ 1	$ 28
Exercised	2	1	24
Exercisable	$ 8	$ 1	$ 14