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Investment Securities - Non-Marketable Securities (Details) |  | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Nov. 27, 2018 | Sep. 30, 2019 USD ($) $ / shares shares | Sep. 30, 2018 USD ($) | Dec. 31, 2018 USD ($) shares | Oct. 24, 2019
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Federal Home Loan Bank stock, par value (in usd per share) | $ / shares |  | $ 100 |  |  |
Conversion rate on common stock | 2 |  |  |  |
Investments in low income housing tax credit funds |  | $ 4,200,000 |  | $ 4,600,000 |
Low income housing tax credits and other tax benefits |  | 480,000 |  |  |
Low income housing amortization expense |  | 381,000 |  |  |
Unfunded commitments for low income housing tax credit funds |  | $ 2,800,000 |  |  |
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 |  | 10,439,000 |
Carrying value of securities carried at cost |  | $ 0 |  | $ 0 |
Fair value of Class B common stock |  | $ 2,900,000 |  | $ 2,200,000 |
Visa Inc. | Visa Inc. Class B common stock |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Conversion rate on common stock |  | 1.6228 |  | 1.6298 |
Other assets |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Federal Home Loan Bank stock |  | $ 11,700,000 |  | $ 11,100,000 |
Subsequent Event |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Federal Home Loan Bank, dividend rate percentage |  |  |  |  | 7.00%
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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- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
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