Securities - Additional Information (Detail) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Schedule of Available-for-sale Securities [Line Items] | |||
| Debt and equity securities OTTI charge | $ 0 | ||
| Impairment charges on securities in continuous unrealized loss position for 12 months or longer | 0 | $ 0 | |
| Net realized gain (loss) on redemption or sale of investment securities | 1,748,000 | 46,000 | $ 6,611,000 |
| Net unrealized gains (losses) recognized in earnings resulting from the redemption of investment securities | (1,300,000) | 314,000 | $ (1,900,000) |
| Investment securities available-for-sale, market values | 578,804,000 | 516,964,000 | |
| Securities Pledged as Collateral [Member] | |||
| Schedule of Available-for-sale Securities [Line Items] | |||
| Investment securities available-for-sale, market values | 130,100,000 | 133,000,000 | |
| Mortgage-backed securities [Member] | |||
| Schedule of Available-for-sale Securities [Line Items] | |||
| Investment securities available-for-sale, market values | $ 303,609,000 | $ 229,630,000 | |
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- Definition Amount of accumulated pre-tax unrealized loss on investments in available-for-sale securities that have been in a loss position for twelve months or longer. No definition available.
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition This element represents the amount of loss recognized for other than temporary impairments (OTTI) of investments in debt and equity securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities and unrealized holding gain (loss) related to transfers of securities into the available-for-sale classification and out of the held-to-maturity classification. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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