Share-Based Compensation Plans - 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
Number of Options
Options outstanding, number of options (in shares)	1,534	1,072
Granted (in shares)	0	521
Exercised (in shares)	(27)	(33)
Forfeited or expired (in shares)	(43)	(26)
Options outstanding, number of options (in shares)	1,464	1,534	1,072
Options exercisable (in shares)	1,012
Options expected to vest (in shares)	437
Weighted-Average Exercise Price Per Share
Beginning options outstanding, weighted average exercise price (in dollars per share)	$ 91.56	$ 94.90
Granted (in dollars per share)	0	82.43
Exercised (in dollars per share)	34.30	42.06
Forfeited or expired (in dollars per share)	99.58	97.82
Ending options outstanding, weighted average exercise price (in dollars per share)	92.33	$ 91.56	$ 94.90
Options exercisable (in dollars per share)	98.27
Options expected to vest (in dollars per share)	$ 79.11
Weighted- Average Remaining Term in Years	5 years 9 months 18 days	6 years 10 months 24 days
Weighted- Average Remaining Term in Years, Options exercisable	5 years 3 months 18 days
Weighted- Average Remaining Term in Years, Options expected to vest	7 years
Aggregate Intrinsic Value	$ 0.0	$ 0.1
Aggregate Intrinsic Value, Options exercisable	0.0
Aggregate Intrinsic Value, Options expected to vest	0.0
Options exercised, aggregate intrinsic value	$ 0.5	$ 1.1	$ 1.7
Options granted, weighted-average grant date fair value (in USD per share)		$ 24.43	$ 19.50