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Pension Plans - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Pension And Other Employee Benefit Plans [Line Items]      
Discount rate 2.69% 3.50%  
Prior service cost $ 0    
Pre-tax unfunded pension obligation gain (loss) $ (1,800,000)    
Asset performance rate of return assumption 6.50%    
Expected long-term return on plan assets 7.00% 7.00% 8.00%
Contribution to pension plan $ 0    
Expense for contribution plan 5,900,000 $ 4,900,000 $ 5,600,000
Expense for the supplemental profit sharing plan 1,100,000 1,100,000 $ 200,000
Supplemental profit sharing plan unfunded status $ 7,100,000 $ 6,100,000  
Decrease in Discount Rate [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Discount rate 0.81%    
Pre-tax unfunded pension obligation gain (loss) $ (5,000,000)    
Gain on Industry Updates to Mortality Table [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) 200,000    
Demographic Changes [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) 200,000    
Asset Performance [Member]      
Pension And Other Employee Benefit Plans [Line Items]      
Pre-tax unfunded pension obligation gain (loss) $ 2,800,000