XML 64 R53.htm IDEA: XBRL DOCUMENT v3.21.2
Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Stock option compensation $ 4.6 $ 4.4
Stock Options Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number exercisable and fully vested 86,836  
Fully vested stock options with performance conditions attached 66,776  
Stock option compensation $ 4.6 4.4
Total intrinsic value exercised 1.8 4.7
Total compensation cost related to non-vested stock options not yet recognized $ 8.8  
Expected compensation cost recognized over the weighted-average period 2 years 7 days  
Stock Equivalent Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Fully vested stock options with performance conditions attached 22,574  
Total intrinsic value exercised $ 1.6 6.3
Expected compensation cost recognized over the weighted-average period 1 year 10 months 20 days  
Number of exercisable SEUs 26,771  
Compensation cost $ 3.4 $ 4.9