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Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock option compensation $ 1.2 $ 1.6
Stock Options Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number exercisable and fully vested 49,444  
Fully vested stock options with performance conditions attached 12,519  
Stock option compensation $ 1.2 1.6
Total intrinsic value exercised 4.2 2.1
Total compensation cost related to non-vested stock options not yet recognized $ 11.9  
Expected compensation cost recognized over the weighted-average period 2 years 1 month 9 days  
Stock Equivalent Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Fully vested stock options with performance conditions attached 56,664  
Total intrinsic value exercised $ 5.6 6.2
Expected compensation cost recognized over the weighted-average period 2 years 4 months 20 days  
Number of exercisable SEUs 63,196  
Compensation cost $ 6.0 $ 7.5