Note 1 - Accounting Policies (Details Textual) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended	19 Months Ended
	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)
Number of Banking Offices	26		26		26
Financing Receivable, Loans Modified During Period					$ 347.0
Financing Receivable, Deferred Payments		$ 2.3
Financing Receivable, Paycheck Protection Program Loans Originated Through the CARES Act			$ 37.2	$ 211.3
SBA CARES Act Paycheck Protection Program [Member]
Financing Receivable, Applications Approved, Amount	$ 364.2		364.2		$ 364.2
Financing Receivable, Deferred Payments, Forgiven Amount	$ 66.9	$ 80.0	$ 254.3