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Loan Servicing - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Jan. 01, 2014
Receivables [Abstract]        
Unpaid principal balances of loans serviced for others totaled $ 1,300,000 $ 1,200,000    
Aggregate fair value of capitalized mortgage servicing rights 12,100 10,800 $ 10,500 $ 7,000
Mortgage servicing rights, net 11,174 8,874 7,642  
Bank recorded additional (impairment) $ (110) $ (59) $ 51