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Employee Benefit Plans (Deferred Compensation Plans) - Additional Information (Detail)
$ in Millions
 12 Months Ended
Dec. 31, 2020
USD ($)
Compensation_Program
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]      
Number of deferred compensation programs | Compensation_Program 4    
Maximum percentage of cash compensation allowed to be deferred under the deferred compensation plan 25.00%    
Criteria for benefit distribution six months after termination of employment in a single lump sum payment or annual installments paid over a three or ten-year term based on the participant’s election    
Benefit distribution, scheduled to be distributed term 6 months    
Deferred compensation income (expense) adjustments due to fair value of the trust assets $ 4.3 $ 3.6 $ (2.1)
Treasury Stock [Member]      
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]      
Common stock, value of shares held by trust $ 2.8    
Minimum [Member]      
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]      
Benefit distribution, paid over annual instalment term 3 years    
Maximum [Member]      
Deferred Compensation Arrangement With Individual Postretirement Benefits [Line Items]      
Benefit distribution, paid over annual instalment term 10 years