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Note 2 - Securities (Details Textual)	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	732	333
Debt Securities, Available-for-Sale, Unrealized Loss Position, Total	$ 573,146,000	$ 461,553,000
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss, Total	83,281,000	9,958,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	0	0
Proceeds from Sale of Debt Securities, Available-for-Sale	0	0	$ 0
Debt Securities, Available-for-Sale, Amortized Cost, Total	685,646,000	597,463,000
Debt Securities, Available-for-Sale, Total	602,936,000	592,743,000
Bonds Issued or Guaranteed by Agencies of the U.S. Federal Government [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss, Total	71,200,000
Bonds Issued by State-based Municipalities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss, Total	12,100,000
State of Michigan and All Its Political Subdivisions [Member]
Debt Securities, Available-for-Sale, Amortized Cost, Total	193,000,000	155,000,000
Debt Securities, Available-for-Sale, Total	182,000,000	158,000,000
All Other States and Their Political Subdivisions [Member]
Debt Securities, Available-for-Sale, Amortized Cost, Total	0	1,700,000
Debt Securities, Available-for-Sale, Total		1,700,000
US Government Agency Debt Obligations and Mortgage Backed Securities [Member]
Debt Securities, Available-for-Sale, Restricted	$ 194,000,000	$ 197,000,000

X

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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