Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Income from continuing operations	$ 61.5	$ 68.5
Less: dividends declared - common stock outstanding, restricted shares and restricted share units	(22.7)	(19.5)
Undistributed earnings	$ 38.8	$ 49.0
Percent allocated to common shareholders	99.30%	99.30%
Undistributed earnings allocated to common shareholders	$ 38.5	$ 48.6
Add: dividends declared - common stock	22.5	19.2
Income from continuing operations attributable to common shares	$ 61.0	$ 67.8
Denominator (in thousands):
Denominator for basic EPS: weighted-average common shares outstanding	64,353	64,018
Effect of dilutive securities:
Performance awards (in shares)	107	325
Stock options (in shares)	388	533
Denominator for diluted EPS: adjusted weighted-average common shares outstanding and assumed conversion	64,848	64,876
Per share income from continuing operations attributable to common shares:
Basic (in dollars per share)	$ 0.95	$ 1.06
Diluted (in dollars per share)	$ 0.94	$ 1.05
Basic weighted-average common shares outstanding	64,353	64,018
Basic weighted-average common shares outstanding, unvested restricted shares expected to vest and restricted share units	64,822	64,491
Percent allocated to common shareholders	99.30%	99.30%
Income (loss) from discontinued operations and net income
Income (loss) from discontinued operations attributable to common shareholders for basic and diluted earnings per share	$ 0.3	$ 0.0
Net income attributable to common shareholders for basic and diluted earnings per share	$ 61.3	$ 67.8
Antidilutive stock options excluded from EPS calculation (in shares)	210	544