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Share-Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted ( in shares) 0 0 0 0
Estimated pretax compensation expense $ 17.0   $ 17.0  
Expiration period in years     4 years  
Performance-based Restricted Stock Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted, Units fair value     $ 4.2 $ 3.9
Granted ( in shares)     400,000 300,000
Service period in years     3 years  
Restricted Stock Units (RSUs) [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted ( in shares) 0 0 400,000 300,000
Granted, Units fair value     $ 4.4 $ 4.4