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Share-Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted ( in shares) 0 0 0 0
Estimated pretax compensation expense $ 28.0   $ 28.0  
Expiration period in years     4 years  
Restricted Stock Units (RSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted ( in shares)   0   0
Granted, Units fair value $ 0.9   $ 4.4  
Restricted Stock Units (RSUs) | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted ( in shares) 100,000   300,000  
Performance-based Restricted Stock Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted, Units fair value     $ 3.9  
Granted ( in shares)       0
Service period in years     3 years  
Performance-based Restricted Stock Units [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Granted ( in shares)     300,000