Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Income from continuing operations	$ 61.8	$ 77.4
Less: dividends declared	(28.3)	(23.3)
Undistributed earnings	$ 33.5	$ 54.1
Percent allocated to common shareholders	99.70%	99.70%
Undistributed earnings available to common shareholders	$ 33.4	$ 53.9
Add: dividends declared on common stock, restricted share units and vested and deferred restricted and performance shares	28.2	23.2
Income from continuing operations attributable to common shares	$ 61.6	$ 77.1
Denominator (in thousands):
Denominator for basic EPS: weighted-average common shares outstanding	55,800,000	57,500,000
Effect of dilutive securities:
Performance awards (in shares)	200,000	100,000
Stock options (in shares)	500,000	300,000
Denominator for diluted EPS: weighted-average shares outstanding	56,500,000	57,900,000
Per share income from continuing operations attributable to common shares:
Basic (in dollars per share)	$ 1.10	$ 1.34
Diluted (in dollars per share)	$ 1.09	$ 1.33
Basic weighted-average common shares outstanding	55,800,000	57,500,000
Basic weighted-average shares outstanding and unvested restricted shares expected to vest	56,000,000.0	57,700,000
Percent allocated to common shareholders	99.70%	99.70%
Income (loss) from discontinued operations and net income
Income from discontinued operations attributable to common shareholders for basic and diluted earnings per share	$ 0.0	$ 2.0
Net income attributable to common shareholders for basic and diluted earnings per share	$ 61.6	$ 79.1
Antidilutive stock options excluded from EPS calculation (in shares)	200,000	300,000