Investment Securities - Additional Information (Detail) (USD $)
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9 Months Ended | 12 Months Ended |
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Sep. 30, 2014
Investmentsecurities
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Dec. 31, 2013
Investmentsecurities
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Investment Securities [Line Items] | ||
Investment securities sold | 0 | 0 |
Investment securities carrying value | $ 81,828,000 | $ 62,064,000 |
Mortgage-backed securities | $ 506,776,000 | |
Life of mortgage-backed securities | 5 years 8 months 12 days | |
Obligations of U.S. government corporations and agencies [Member]
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Investment Securities [Line Items] | ||
Debt securities | 13 | |
Percentage of aggregate depreciation in unrealized losses | 1.79% | |
Obligations of states and political subdivisions [Member]
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Investment Securities [Line Items] | ||
Debt securities | 10 | |
Percentage of aggregate depreciation in unrealized losses | 1.62% | |
Corporate debt securities [Member]
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Investment Securities [Line Items] | ||
Debt securities | 0 |