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Securities - Additional Information (Detail) (USD $) | 9 Months Ended | 12 Months Ended
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Sep. 30, 2014 Obligation Securities | Dec. 31, 2013 Obligation Securities
Amortized Cost and Fair Value Debt Securities [Abstract] |  |
Number of U.S. agency and mortgage-backed securities in an unrealized loss position | 34 | 40
Number of obligations of state and political subdivisions in an unrealized loss position | 16 | 21
Percentage of investment portfolio | 100.00% | 100.00%
Weighted-average period of re-pricing of portfolio | 4 years | 4 years 6 months
Impairment recognized | $ 0 |

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- Definition Impairment losses related to federal home loan stock. + References No definition available. + Details
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