Annual report pursuant to Section 13 and 15(d)

Selected Balance Sheet Data - Additional Information (Detail)

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Selected Balance Sheet Data - Additional Information (Detail)
 12 Months Ended
Jan. 01, 2019
Jan. 01, 2018
Jan. 01, 2017
Jan. 01, 2014
Dec. 31, 2019
USD ($)
Installments
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Mar. 31, 2013
USD ($)
Schedule Of Accrued Expenses [Line Items]                
SARs frozen liability amount         $ 18,122,000 $ 19,299,000    
Interest expense         $ 1,388,000 1,400,000 $ 1,496,000  
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         $ 1,600,000,000 1,600,000,000    
Escrow Funds         $ 2,600,000 2,100,000    
SARs [Member]                
Schedule Of Accrued Expenses [Line Items]                
SARs frozen liability amount               $ 20,000,000.0
SARs liability frozen value date         Mar. 31, 2013      
SARs liability number of annual installments | Installments         10      
SARs liability interest accrual commencement date         Jan. 01, 2014      
SARs liability interest accrual rates 4.684% 4.409% 4.446%          
Interest expense         $ 904,000 891,000 $ 931,000  
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         $ 1,800,000 1,700,000    
Sars liability principal paid         185,000      
Sars liability interest paid         $ 1,600,000      
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 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         $ 1,600,000 $ 1,300,000