Annual report pursuant to Section 13 and 15(d)

Loans and Leases - Additional Information (Detail)

v3.8.0.1
Loans and Leases - Additional Information (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
Property
SecurityLoan
Dec. 31, 2016
USD ($)
Property
Dec. 31, 2015
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accrued interest receivable $ 12,770 $ 10,987  
Loans receivable 4,273,415 3,812,340  
Reclassification from loans receivable to loans held for sale 0 0 $ 360
Sale of loans held for sale $ 111,977 $ 84,901  
Number of real estate properties | Property 6 12  
Net carrying value of other real estate property $ 1,946 $ 7,484  
TDR loans receivable $ 15,400 18,000 17,200
Principal and interest due 6 months    
Reserves relating to loans included in allowance for loan losses $ 2,200 3,400 $ 1,000
Number of loans restructured | SecurityLoan 4    
Serviced loans sold to unaffiliated parties $ 476,500 484,700  
Central Bancorp, Inc [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Net carrying value of other real estate property 1,800 5,700  
Securities Pledged as Collateral [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Loans receivable 1,100,000 1,000,000  
Residential Real Estate [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Net carrying value of other real estate property 1,100    
Loans and Finance Receivables [Member]      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accrued interest receivable $ 10,200 $ 8,200