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Investment Securities - Non-marketable Securities (Details)		1 Months Ended	12 Months Ended
	Nov. 27, 2018	Oct. 31, 2018 USD ($) shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Feb. 21, 2019
Marketable Securities [Line Items]
Federal Home Loan Bank stock, par value (usd per share) | $ / shares			$ 100
Stock split ratio	2
Investments in low income housing tax credit funds			$ 4,600,000	$ 2,100,000
Low income housing tax credits and other tax benefits			597,000
Low income housing amortization expense			507,000
Unfunded commitments for low income housing tax credit funds			3,100,000
Catch-up amortization expense due to tax reduction				67,000
Other assets
Marketable Securities [Line Items]
Federal Home Loan Bank stock			$ 11,100,000	$ 11,100,000
Visa Inc. Class B Common Stock
Marketable Securities [Line Items]
Number of shares of securities carried at cost (in shares) | shares			10,439	16,939
Fair value of Class B common stock			$ 0
Equity securities			$ 2,200,000	$ 3,200,000
Shares of Visa Inc. Class B restricted common stock (in shares) | shares		6,500
Gain from sale of Visa Inc. Class B restricted common stock		$ 956,000
Visa Inc. | Visa Inc. Class B common stock
Marketable Securities [Line Items]
Stock split ratio			1.6298	1.6483
Subsequent event
Marketable Securities [Line Items]
Federal Home Loan Bank, dividend rate percentage					7.00%

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