Stock-Based Compensation (Stock Options) (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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]
Exercised, shares	(0.4)	(0.5)	(1.0)
Exercised, weighted-average exercise price (in dollars per share)	$ 33.87	$ 35.25	$ 37.85
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period (in years)	10 years
Vesting period (in years)	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning balance (in shares)	3.1
Options outstanding, weighted-average exercise price, beginning balance (in dollars per share)	$ 50.20
Granted, shares	0.0
Granted, weighted-average exercise price (in dollars per share)	$ 0
Exercised, shares	(0.4)
Exercised, weighted-average exercise price (in dollars per share)	$ 33.87
Forfeited, shares	0.0
Forfeited, weighted-average exercise price (in dollars per share)	$ 0
Expired, shares	(0.1)
Expired, weighted-average exercise price (in dollars per share)	$ 55.35
Options outstanding, ending balance (in shares)	2.6	3.1
Options outstanding, weighted-average exercise price, ending balance (in dollars per share)	$ 52.29	$ 50.20
Options outstanding, weighted-average remaining contractual term (years)	4 years 5 months 26 days
Options outstanding, aggregate intrinsic value	$ 5.7
Options exercisable (in shares)	2.4
Options exercisable, weighted-average exercise price (in dollars per share)	$ 52.28
Options exercisable, weighted-average remaining contractual term (years)	4 years 4 months 20 days
Options exercisable, aggregate intrinsic value	$ 5.7
Options exercisable and expected to vest thereafter (in shares)	2.6
Options exercisable and expected to vest thereafter, weighted-average exercise price (in dollars per share)	$ 52.29
Options exercisable and expected to vest thereafter, weighted-average remaining contractual term (years)	4 years 5 months 26 days
Options exercisable and expected to vest thereafter, aggregate intrinsic value	$ 5.7
Options available for future grants (in shares)	3.9
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Total intrinsic value of stock options exercised	$ 5.2	$ 8.2	$ 11.9