Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Income from continuing operations	$ 255.2	$ 113.0	$ 745.4	$ 256.2
Less: dividends declared	39.1	28.4	95.8	84.4
Undistributed earnings	$ 216.1	$ 84.6	$ 649.6	$ 171.8
Percent allocated to common stockholders	99.80%	99.70%	99.80%	99.70%
Undistributed earnings allocated to common stockholders	$ 215.6	$ 84.3	$ 648.0	$ 171.3
Add: dividends declared to common shares, restricted share units and vested and deferred restricted and performance shares	39.0	28.2	95.6	84.1
Income from continuing operations attributable to common stockholders	$ 254.6	$ 112.5	$ 743.6	$ 255.4
Shares:
Basic weighted-average shares outstanding (in shares)	51.9	52.3	51.9	52.6
Effect of dilutive securities:
Performance awards (in shares)	0.2	0.2	0.2	0.1
Stock options (in shares)	0.5	0.5	0.5	0.5
Diluted weighted-average shares outstanding (in shares)	52.6	53.0	52.6	53.2
Per share income from continuing operations attributable to common shares:
Basic (in dollars per share)	$ 4.91	$ 2.15	$ 14.32	$ 4.86
Diluted (in dollars per share)	$ 4.84	$ 2.12	$ 14.12	$ 4.80
Basic weighted-average shares outstanding (in shares)	51.9	52.3	51.9	52.6
Basic weighted-average shares outstanding and unvested restricted shares expected to vest (in shares)	52.0	52.4	52.0	52.7
Percent allocated to common stockholders	99.80%	99.70%	99.80%	99.70%
Anti-dilutive stock options excluded from EPS calculation
(Loss) income from discontinued operations attributable to common stockholders for basic and diluted earnings per share	$ (0.5)	$ 29.0	$ 4.4	$ 37.3
Net income attributable to common stockholders for basic and diluted earnings per share	$ 254.1	$ 141.5	$ 748.0	$ 292.7
Anti-dilutive stock options excluded from earnings per share calculation (in shares)	0.0	0.0	0.1	0.2