Earnings Per Share (Reconciliation of Earnings (loss) to Earnings (loss) Attributable to Common Shares Used in Basic and Diluted Calculation) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Earnings (loss) from continuing operations	$ 54.2	$ 90.7	$ (118.9)	$ 190.8
(Earnings) allocated to participating vested share awards	(0.1)	(0.2)	(0.1)	(0.4)
Earnings (loss) from continuing operations attributable to common shares	$ 54.1	$ 90.5	$ (119.0)	$ 190.4