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Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock option compensation $ 1.6 $ 1.2
Stock Options Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number exercisable and fully vested 115,847  
Fully vested stock options with performance conditions attached 77,979  
Stock option compensation $ 1.6 1.2
Total intrinsic value exercised 0.6 4.2
Total compensation cost related to non-vested stock options not yet recognized $ 12.1  
Expected compensation cost recognized over the weighted-average period 2 years 2 months 19 days  
Stock Equivalent Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Fully vested stock options with performance conditions attached 40,464  
Total intrinsic value exercised $ 0.3 5.6
Expected compensation cost recognized over the weighted-average period 2 years 3 months 3 days  
Number of exercisable SEUs 52,279  
Compensation cost $ 4.4 $ 6.0