v3.26.1
Calculation of Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Earnings Per Share [Abstract]    
Income (Loss) from Continuing Operations, Per Basic Share $ 2.48  
Calculation of Basic Earnings Per Share:    
Net Income $ 59.3 $ 50.9
Weighted shares outstanding (shares) [1] 23,937 22,957
Basic Earnings Per Share (in dollars per share) $ 2.48 $ 2.22
Reconciliation of Numerator:    
Net Income $ 59.3 $ 50.9
Reconciliation of Denominator:    
Weighted shares outstanding - Basic (shares) [1] 23,937 22,957
Effect of dilutive securities:    
Share-based compensation (shares) 116 84
Adjusted denominator-Diluted (shares) 24,053 23,041
Income (Loss) from Continuing Operations, Per Diluted Share $ 2.47 $ 2.21
Diluted Earnings Per Share (in dollars per share) $ 2.47 $ 2.21
Net Income $ 59.3 $ 50.9
Basic (shares) [1] 23,937 22,957
Income (Loss) from Continuing Operations, Per Basic Share $ 2.48  
Basic (in dollars per share) $ 2.48 $ 2.22
Share-based compensation (shares) 116 84
Diluted (shares) 24,053 23,041
Income (Loss) from Continuing Operations, Per Diluted Share $ 2.47 $ 2.21
Diluted (in dollars per share) $ 2.47 $ 2.21
Retained Earnings [Member]    
Calculation of Basic Earnings Per Share:    
Net Income $ 59.3 $ 50.9
Reconciliation of Numerator:    
Net Income 59.3 50.9
Net Income $ 59.3 $ 50.9
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