Quarterly report pursuant to Section 13 or 15(d)

Selected Balance Sheet Data - Additional Information (Detail)

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Selected Balance Sheet Data - Additional Information (Detail) - USD ($)
 3 Months Ended 6 Months Ended
Jan. 01, 2021
Jan. 01, 2020
Jan. 01, 2014
Jun. 30, 2022
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2021
Dec. 31, 2021
Mar. 31, 2013
Schedule Of Accrued Expenses [Line Items]                  
SARs frozen liability amount       $ 12,866,000   $ 12,866,000   $ 14,918,000  
Interest expense       158,000 $ 146,000 $ 318,000 $ 292,000    
Treasury note term           1 year      
Advances and loans and commissions receivable allowance for credit loss       1,110,000   $ 1,110,000   794,000  
Commissions Payable [Member]                  
Schedule Of Accrued Expenses [Line Items]                  
Estimated payouts description           Commissions that are not expected to be paid within twelve months are classified as long-term.      
Maximum payment deferral period for certain commissions payable           3 years      
Mortgage servicing rights [Member]                  
Schedule Of Accrued Expenses [Line Items]                  
Servicing portfolio of commercial real estate loans, unpaid principal balance               $ 1,700,000,000  
SARs [Member]                  
Schedule Of Accrued Expenses [Line Items]                  
SARs frozen liability amount                 $ 20,000,000
SARs liability frozen value date           Mar. 31, 2013      
SARs liability interest accrual commencement date           Jan. 01, 2014      
SARs liability interest accrual rates 2.93% 3.63%              
Interest expense       $ 136,000 $ 122,000 $ 271,000 244,000    
Treasury note term     10 years            
Base spread on SARs liability variable rate     2.00%            
Estimated payouts description           Estimated payouts within the next twelve months for participants that have separated from service have been classified as current.      
Payments made during the period           $ 2,200,000 2,200,000    
Deferred Compensation Liability [Member]                  
Schedule Of Accrued Expenses [Line Items]                  
Estimated payouts description           Estimated payouts within the next twelve months for participants that have separated from service or elected an in-service payout have been classified as current.      
Deferred Compensation Liability, Minimum Payout Period           2 years      
Deferred Compensation Liability, Maximum Payout Period           15 years      
Fair value of deferred compensation plan assets           110.00%      
Payments made during the period           $ 625,000 $ 815,000