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Investment Securities - Additional Information (Detail) (USD $)
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6 Months Ended |
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Jun. 30, 2012
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Dec. 31, 2011
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| Investment [Line Items] |
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| Number of investment positions in continuous loss position |
23 |
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| Available-for-sale Securities, amortized cost |
$ 122,437,000 |
$ 108,921,000 |
| Available-for-sale Securities, fair value |
125,029,000 |
111,440,000 |
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Government and Agencies Debt Securities
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| Investment [Line Items] |
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| Number of investment positions in continuous loss position |
21 |
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| Percentage amount by which investment positions in continuous loss position had depreciated from amortized cost basis |
0.50% |
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Collateralized Mortgage Obligations Issued By Private Enterprise
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| Investment [Line Items] |
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| Percentage amount by which investment positions in continuous loss position had depreciated from amortized cost basis |
20.10% |
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| Available-for-sale Securities, amortized cost |
720,000 |
896,000 |
| Available-for-sale Securities, fair value |
684,000 |
880,000 |
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Collateralized Mortgage Obligations Issued By Private Enterprise | Securities Downgraded To Substandard
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| Investment [Line Items] |
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| Available-for-sale Securities, amortized cost |
243,000 |
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| Available-for-sale Securities, fair value |
$ 194,000 |
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