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Investment Securities - Non-Marketable Securities Included in Other Assets (Details) | 9 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 USD ($) $ / shares shares | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($) shares | Oct. 28, 2021
Schedule of Equity Method Investments [Line Items] |  |  |  |
Federal home loan bank stock, par value (in usd per share) | $ / shares | $ 100 |  |  |
Investments in low income housing tax credit funds | $ 3,200,000 |  | $ 3,500,000 |
Low income housing tax credits and other tax benefits | 484,000 |  |  |
Low income housing amortization expense | 406,000 |  |  |
Unfunded commitments for low income housing tax credit funds | $ 425,000 |  |  |
Subsequent event |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Federal home loan bank, dividend rate percentage |  |  |  | 6.00%
Visa Inc. Class B common stock |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Number of shares of securities carried at cost (in shares) | shares | 10,439 |  | 10,439 |
Carrying value of securities carried at cost | $ 0 |  | $ 0 |
Fair value of Class B common stock | $ 3,800,000 |  | $ 3,700,000 |
Visa Inc. | Visa Inc. Class B common stock |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Conversion rate on common stock | 1.6228 |  | 1.6228 |
Asset Derivatives |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Federal home loan bank stock | $ 16,700,000 |  | $ 11,900,000 |
Low-income housing tax credit investment |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Impairment losses | $ 0 | $ 0 |  |

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- Definition Amortization Method Qualified Affordable Housing Project Investments, Tax Credits + References No definition available. + Details
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- Definition Amount of investment in qualified affordable housing projects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 740 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116633289&loc=SL49122993-202985 + Details
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