Earnings Per Share (Reconciliation of Net Earnings to Net Earnings Attributable to Common Shares Used in Basic and Diluted Calculation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings from continuing operations	$ 220.6	$ 99.3	$ 57.9
Earnings allocated to participating non-vested share awards	(0.7)	(0.3)	(0.2)
Earnings from continuing operations attributable to common shares	$ 219.9	$ 99.0	$ 57.7