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Investment Securities - Additional Information (Detail) (USD $)
 12 Months Ended 3 Months Ended 3 Months Ended
Dec. 31, 2013
Securities
Mar. 31, 2014
Securities
Mar. 31, 2014
Non Agency Mortgage Backed Securities
Mar. 31, 2013
Non Agency Mortgage Backed Securities
Mar. 31, 2014
Mortgage-backed securities Non-Agency Alt-A residential
Mar. 31, 2014
Equity Securities
Mar. 31, 2013
Equity Securities
Mar. 31, 2014
Debt Securities
Mar. 31, 2013
Debt Securities
Schedule of Available-for-sale Securities [Line Items]                  
Held-to-maturity securities in continuous unrealized loss position $ 0                
Number of securities in an unrealized loss position 219 149              
Percentage of combined depreciation of the combined reported value of the aggregate securities portfolio 5.06% 4.30%              
Carrying value of securities pledged 284,770,000 284,590,000              
OTTI charges incurred     $ 232,000 $ 0   $ 32,000 $ 0 $ 0 $ 0
Voluntary constant prepayment rate         2.50%        
Constant default rate scenario         15.00%        
Severity rate         51.00%        
Reduced severity rate   10.00%              
Severity rate reduction period   33 months