Note 2 - Securities (Details Textual)	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	774	333
Debt Securities, Available-for-Sale, Unrealized Loss Position, Total	$ 574,303,000	$ 461,553,000
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss, Total	91,769,000	9,958,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	0	0
Debt Securities, Available-for-Sale, Amortized Cost, Total	674,725,000	597,463,000
Debt Securities, Available-for-Sale, Total	582,999,000	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	74,600,000
Bonds Issued by State-based Municipalities [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss, Total	17,200,000
State of Michigan and All Its Political Subdivisions [Member]
Debt Securities, Available-for-Sale, Amortized Cost, Total	181,000,000	155,000,000
Debt Securities, Available-for-Sale, Total	164,000,000	158,000,000
All Other States and Their Political Subdivisions [Member]
Debt Securities, Available-for-Sale, Amortized Cost, Total	200,000	1,700,000
Debt Securities, Available-for-Sale, Total	300,000	1,700,000
US Government Agency Debt Obligations and Mortgage Backed Securities [Member]
Debt Securities, Available-for-Sale, Restricted	$ 199,000,000	$ 197,000,000