Quarterly report pursuant to Section 13 or 15(d)

Loans - Additional Information (Detail)

v3.4.0.3
Loans - Additional Information (Detail)
 3 Months Ended
Mar. 31, 2016
USD ($)
SecurityLoan
Property
Mar. 31, 2015
USD ($)
Dec. 31, 2015
USD ($)
Property
Dec. 31, 2014
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accrued interest receivable $ 10,626,000   $ 9,501,000  
Loans receivable 3,265,453,000   $ 3,140,381,000  
Transfer of loans receivable to loans held for sale $ 0 $ 0    
Number of real estate properties | Property 17   14  
Other real estate owned (OREO), net $ 9,411,000   $ 8,511,000  
TDR loans receivable $ 16,300,000   17,200,000  
Principal and interest due 3 months      
Reserves relating to loans included in allowance for loan losses $ 900,000   1,000,000  
Number of loans restructured | SecurityLoan 3      
PCI Loans [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans receivable $ 14,190,000 $ 39,505,000 14,573,000 $ 43,475,000
Outstanding balance of PCI loans - the undiscounted sum of all amounts including amounts deemed principal, interest, fees and penalties 29,500,000   30,900,000  
Central Bancorp, Inc [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Other real estate owned (OREO), net 6,900,000   7,400,000  
Securities Pledged as Collateral [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans receivable 518,900,000   557,700,000  
Residential Properties [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Other real estate owned (OREO), net 229,000      
Loans and Finance Receivables [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accrued interest receivable $ 7,100,000   $ 7,900,000