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Investment in Securities (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Investments, Debt and Equity Securities [Abstract] |  |  |
Number of securities that had an unrealized loss | 64 | 108 |
Number of securities that had an unrealized loss, greater than 12 months | 24 |  |
Percentage of total securities | 17.00% |  |
Premium related to purchase of state and political subdivisions | $ 7,147 | $ 5,749 |
Securities pledged as collateral | 3,750 | 3,750 |
Proceeds from sales of securities available-for-sale |  | 21,491 | $ 99,347
Gross realized gains | 0 | 387 | 2,910
Gross realized losses | $ 0 | $ 0 | $ 0

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- Definition The premium related to the purchase of state and political subdivisions. + References No definition available. + Details
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- Definition This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563 + Details
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- Definition The fair value of available-for-sale securities that serve as collateral for borrowings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5086-111524 + Details
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