Quarterly report pursuant to Section 13 or 15(d)

Selected Balance Sheet Data - Additional Information (Detail)

v3.19.1
Selected Balance Sheet Data - Additional Information (Detail)
 3 Months Ended
Jan. 01, 2019
Jan. 01, 2018
Jan. 01, 2014
Mar. 31, 2019
USD ($)
Installments
Mar. 31, 2018
USD ($)
Dec. 31, 2018
USD ($)
Mar. 31, 2013
USD ($)
Schedule Of Accrued Expenses [Line Items]              
Servicing portfolio of commercial real estate loans, unpaid principal balance       $ 1,600,000,000   $ 1,600,000,000  
SARs frozen liability amount       17,630,000   19,299,000  
Interest expense       $ 349,000 $ 360,000    
Maximum payment deferral period for certain commissions payable       3 years      
Mortgage servicing rights [Member]              
Schedule Of Accrued Expenses [Line Items]              
Escrow Funds       $ 2,200,000   $ 2,100,000  
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 number of annual installments | Installments       10      
SARs liability interest accrual commencement date       Jan. 01, 2014      
SARs liability interest accrual rates 4.684% 4.409%          
Interest expense       $ 226,000 225,000    
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       $ 1,700,000 1,500,000    
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 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       $ 315,000 $ 193,000