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Investment Securities - Non-marketable Securities (Details)		12 Months Ended
	Nov. 27, 2018	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Feb. 18, 2021
Marketable Securities [Line Items]
Federal Home Loan Bank stock, par value (usd per share) | $ / shares		$ 100
Stock split ratio	2
Shares of Visa Inc. Class B restricted common stock sold (in shares) | shares				6,500
Gain from sale of Visa Inc. Class B restricted common stock				$ 956,000
Investments in low income housing tax credit funds		$ 3,500,000	$ 4,100,000
Low income housing tax credits and other tax benefits		654,000
Low income housing amortization expense		550,000
Unfunded commitments for low income housing tax credit funds		821,000
Other assets
Marketable Securities [Line Items]
Federal Home Loan Bank stock		$ 11,900,000	$ 11,700,000
Visa Inc. Class B Common Stock
Marketable Securities [Line Items]
Number of shares of securities carried at cost (in shares) | shares		10,439	10,439
Fair value of Class B common stock		$ 0	$ 0
Equity securities		$ 3,700,000	$ 3,200,000
Visa Inc. | Visa Inc. Class B common stock
Marketable Securities [Line Items]
Stock split ratio		1.6228	1.6228
Subsequent event
Marketable Securities [Line Items]
Federal Home Loan Bank, dividend rate percentage					5.00%

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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).

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