Earnings per Share - Reconciliation of Numerator and Denominator of Basic and Diluted Earnings per Share Calculation and Anti-dilutive Share-based Awards (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share Basic And Diluted [Line Items]
Basic	$ 1.46	$ 1.27	$ 2.25	$ 2.32
Diluted	$ 1.42	$ 1.24	$ 2.17	$ 2.26
Net earnings	$ 46.0	$ 42.9	$ 72.4	$ 78.1
Basic weighted average number of common shares outstanding	31.5	33.7	32.2	33.6
Dilutive awards	0.9	0.8	1.2	0.9
Diluted weighted average number of common shares outstanding	32.4	34.5	33.4	34.5
Restricted stock units
Earnings Per Share Basic And Diluted [Line Items]
Total weighted average number of anti-dilutive share-based awards	0.0	0.0	0.0	0.3