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Employee Savings Plans - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Expenses related ESOP $ 12,300 $ 10,300 $ 10,000
Shares vested under ESOP 3,242,000    
Matching percentage of employer to employee contributions 100.00%    
Matching contributions to 401(k) retirement savings plan $ 26,900 26,200 $ 24,500
Temporary equity, shares issued (in shares) 129,457    
Deferred compensation $ 12,300 13,600  
Temporary equity, other changes 11,300    
Temporary equity, accretion to redemption value, adjustment $ 1,000    
Employee Stock Ownership Plan E S O P Plan      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Maximum number of shares of common stock available for issuance 7,700,000    
Fair value, measurements, recurring      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Total assets at fair value $ 48,300    
Level 1 | Fair value, measurements, recurring      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Total assets at fair value 48,300    
Level 1 | Fair value, measurements, recurring | Non-qualified deferred compensation assets      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Total assets at fair value $ 48,300 $ 48,900  
Share-based Compensation Award, Tranche One      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
ESOP vesting period 2 years    
Share-based Compensation Award, Tranche Two      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
ESOP vesting period 3 years