Net Earnings Per Common Share - Computations of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net earnings	$ 84.8	$ 78.9	$ 167.4	$ 156.5
Weighted average common shares - basic	100.2	104.5	100.7	104.5
Effect of restricted shares issued	0.5	0.5	0.4	0.5
Diluted weighted average common shares	100.7	105.0	101.1	105.0
Net earnings per share from continuing operatings - basic (in dollars per share)	$ 0.85	$ 0.76	$ 1.66	$ 1.50
Net earnings per share - basic (in dollars per share)	0.85	0.76	1.66	1.50
Net earnings per share from continuing operations - diluted	0.84	0.75	1.66	1.49
Diluted net earnings per share (in dollars per share)	$ 0.84	$ 0.75	$ 1.66	$ 1.49