Net Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net earnings	$ 506.8	$ 502.9	$ 263.0
Distributed and allocated undistributed net earnings to unvested restricted stockholders	0.0	(0.2)	(0.5)
Net Income (Loss) Available to Common Stockholders, Basic, Total	$ 506.8	$ 502.7	$ 262.5
Denominator
Weighted average number of common shares outstanding - basic (in shares)	150.9	155.2	154.3
Basic net earnings per common share
Basic net earnings per common share (in dollars per share)	$ 3.36	$ 3.24	$ 1.70
Numerator:
Net earnings available to common stockholders	$ 506.8	$ 502.7	$ 262.5
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	150.9	155.2	154.3
Effect of dilutive stock shares and units (in shares)	1.5	0.8	0.5
Weighted average number of common shares outstanding - diluted under two-class (in shares)	152.4	156.0	154.8
Effect of unvested restricted stock - participating security (in shares)	0.0	0.0	0.4
Weighted average number of common shares outstanding - diluted under treasury stock (in shares)	152.4	156.0	155.2
Diluted net earnings per common share - (in dollars per share)	$ 3.32	$ 3.22	$ 1.69
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Diluted (in shares)	152.4	156.0	155.2
PSU Awards
Denominator:
Weighted average number of common shares outstanding - diluted under treasury stock (in shares)	0.6
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Diluted (in shares)	0.6