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Investment Securities - Non-Marketable Securities (Details)	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares	Apr. 28, 2016	Dec. 31, 2015 USD ($)
Schedule of Cost-method Investments [Line Items]
Federal Home Loan Bank stock, par value | $ / shares	$ 100
Investments in low income housing tax credit funds	$ 2,600,000		$ 2,700,000
Low income housing tax credits and other tax benefits	82,000
Low income housing amortization expense	63,000
Unfunded commitments for low income housing tax credit funds	$ 1,700,000
Visa Inc. | Visa Inc. Class B common stock
Schedule of Cost-method Investments [Line Items]
Stockholders' Equity Note, Stock Split, Conversion Ratio	1.6483
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	2,100,000		$ 2,200,000
Subsequent event
Schedule of Cost-method Investments [Line Items]
Federal Home Loan Bank, dividend rate percentage		8.90%
Other assets
Schedule of Cost-method Investments [Line Items]
Federal Home Loan Bank stock	$ 8,400,000

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