Net Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Numerator:
Net earnings	$ 99.1	$ 113.9	$ 161.0	$ 263.1
Distributed and allocated undistributed net earnings to unvested restricted stockholders	0.0	0.0	0.0	0.0
Net earnings available to common stockholders	$ 99.1	$ 113.9	$ 161.0	$ 263.1
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	144.5	146.0	144.3	146.8
Basic net earnings per common share:
Basic net earnings per common share (in dollars per share)	$ 0.69	$ 0.78	$ 1.12	$ 1.79
Numerator:
Net earnings available to common stockholders	$ 99.1	$ 113.9	$ 161.0	$ 263.1
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	144.5	146.0	144.3	146.8
Effect of unvested restricted stock units (in shares)	0.3	1.5	0.5	1.7
Weighted average number of common shares outstanding - diluted under treasury stock (in shares)	144.8	147.5	144.8	148.5
Diluted net earnings per common share (in dollars per share)	$ 0.68	$ 0.77	$ 1.11	$ 1.77