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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 |  |  |  |  |  |  |

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