Stock-Based Compensation Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Aggregate value	$ 9	$ 12	$ 15
Cash received for exercise price	$ 59	$ 56	$ 107
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance	4,027,652
Options exercised	(1,388,165)
Options expired	(750,442)
Ending Balance	1,889,045	4,027,652
Exercisable at December 31, 2019	1,889,045
Weighted Average Exercise Price (in usd per share)	$ 40.43	$ 43.95
Options Exercised, Weighted Average Exercise Price (in usd per share)	42.25
Options Expired, Weighted Average Exercise Price (in usd per share)	55.96
Shares Exercisable, Weighted Average Exercise Price (in usd per share)	$ 40.43
Shares Outstanding, Weighted Average Remaining Contractual Life	1 year 6 months 21 days	2 years 10 months 24 days
Shares Exercisable, Weighted Average Remaining Contractual Life	1 year 6 months 21 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 10	$ 14
Shares Exercisable, Aggregate Intrinsic Value	$ 10