Quarterly report pursuant to Section 13 or 15(d)

Acquisition - Additional Information (Detail)

v3.3.0.814
Acquisition - Additional Information (Detail)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Aug. 31, 2014
USD ($)
branch
$ / shares
Sep. 30, 2015
USD ($)
Sep. 30, 2014
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2014
USD ($)
Dec. 31, 2014
USD ($)
Loans At Acquisition Date [Line Items]            
Bargain purchase gain, net of deferred taxes   $ 0 $ 14,577 $ 0 $ 14,577  
Merger and integration expense   0 3,415 1,747 3,572  
Amortization of subordinated debentures   46   125    
Central Bancorp, Inc [Member]            
Loans At Acquisition Date [Line Items]            
Common stock, price per share after acquisition | $ / shares $ 17.64          
Consideration paid $ 50,000          
Consideration paid for redemption of preferred stock and cumulative unpaid dividends 28,675          
Total assets acquired 1,267,921          
Total liabilities assumed 1,174,669          
Total identifiable net assets 93,252          
Loans 297,272          
Total deposits $ 1,098,997          
Number of branch locations | branch 23          
Bargain purchase gain, net of deferred taxes $ 14,577          
Merger and integration expense   0   1,700   $ 6,600
Core deposit intangible $ 2,213          
Core deposit intangible, useful life 10 years          
Amortization expense of core deposit intangible   95   285    
Certificates of deposit $ 11,300          
Amortization of certificates of deposit   1,400   4,500    
Central Bancorp, Inc [Member] | Subordinated Debentures [Member]            
Loans At Acquisition Date [Line Items]            
Discount on subordinated debentures $ 8,300   $ 8,300   $ 8,300  
Amortization of subordinated debentures   $ 46   $ 125