Net Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net earnings	$ 149.2	$ 110.1
Distributed and allocated undistributed net earnings to unvested restricted stockholders	0.0	0.0
Net earnings available to common stockholders	$ 149.2	$ 110.1
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	147.6	154.1
Basic net earnings per common share:
Basic net earnings per common share (in dollars per share)	$ 1.01	$ 0.71
Numerator:
Net earnings available to common stockholders	$ 149.2	$ 110.1
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	147.6	154.1
Effect of unvested restricted stock units (in shares)	1.9	1.3
Weighted average number of common shares outstanding - diluted under treasury stock (in shares)	149.5	155.4
Diluted net earnings per common share (in dollars per share)	$ 1.00	$ 0.71