Annual report pursuant to Section 13 and 15(d)

Loans - Additional Information (Detail)

v3.3.1.900
Loans - Additional Information (Detail)
 3 Months Ended 12 Months Ended
Sep. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Property
SecurityLoan
Dec. 31, 2014
USD ($)
Property
Dec. 31, 2013
USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accrued interest receivable   $ 9,501,000 $ 9,749,000  
Loans receivable   3,140,381,000 2,735,832,000  
Reclassification from loans receivable to loans held for sale   360,000 0 $ 8,010,000
Sale of loans held for sale   89,471,000 42,412,000  
Allowance for off-balance sheet items   $ 1,000,000 $ 1,400,000  
Number of real estate properties | Property   14 27  
Net carrying value of other real estate property   $ 8,511,000 $ 15,790,000  
TDR loans receivable   $ 17,200,000 26,300,000 30,000,000
Principal and interest due   6 months    
Reserves relating to loans included in allowance for loan losses   $ 1,000,000 2,900,000 $ 2,800,000
Number of loans restructured | SecurityLoan   14    
Serviced loans sold to unaffiliated parties   $ 474,000,000 500,900,000  
Insurance reimbursement settlement $ 611,000,000      
Recoveries of previously charged-off and reimbursed Commercial SLA loans which needs to be reimbursed   95.00%    
FDIC recovery period   3 years    
Federal Deposit Insurance Corporation (FDIC) loss sharing liability   $ 1,289,000 2,074,000  
FDIC recoveries partially offset   2,300,000    
Reimbursable expense owed to bank   1,000,000    
Non-Single Family SLA [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Federal Deposit Insurance Corporation (FDIC) loss sharing liability   1,300,000    
Single Family SLA [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Federal Deposit Insurance Corporation (FDIC) loss sharing liability   0    
Minimum [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Recoveries of previously charged-off and reimbursed Commercial SLA loans which needs to be reimbursed 80.00%      
Maximum [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Recoveries of previously charged-off and reimbursed Commercial SLA loans which needs to be reimbursed 95.00%      
Central Bancorp, Inc [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Net carrying value of other real estate property   7,400,000 15,300,000  
Securities Pledged as Collateral [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Loans receivable   557,700,000 840,000,000  
Residential Real Estate [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Net carrying value of other real estate property   3,000,000    
Loans and Finance Receivables [Member]        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accrued interest receivable   $ 7,900,000 $ 6,400,000