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Investment Securities - Non-marketable Securities (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2017 USD ($) $ / shares shares | Feb. 21, 2018 | Dec. 31, 2016 USD ($)
Schedule of Cost-method Investments [Line Items] |  |  |
Federal Home Loan Bank stock, par value (usd per share) | $ / shares | $ 100 |  |
Investments in low income housing tax credit funds | $ 2,100,000 |  | $ 2,500,000
Low income housing tax credits and other tax benefits | 332,000 |  |
Low income housing amortization expense | 331,000 |  |
Unfunded commitments for low income housing tax credit funds | 546,000 |  |
Catch-up amortization expense due to tax reduction | $ 67,000 |  |
Subsequent event |  |  |
Schedule of Cost-method Investments [Line Items] |  |  |
Federal Home Loan Bank, dividend rate percentage |  | 7.00% |
Visa Inc. Class B common stock |  |  |
Schedule of Cost-method Investments [Line Items] |  |  |
Number of shares of securities carried at cost | shares | 16,939 |  |
Carrying value of securities carried at cost | $ 0 |  |
Fair value of Class B common stock | $ 3,200,000 |  | 2,200,000
Conversion ratio for common stock | 1.6483 |  |
Other assets |  |  |
Schedule of Cost-method Investments [Line Items] |  |  |
Federal Home Loan Bank stock | $ 11,100,000 |  | $ 10,200,000

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- Definition Amount of investment in qualified affordable housing projects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985 + Details
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