Note 4 - Loans and Allowance for Credit Losses on Loans (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 01, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Loans and Leases Receivable, Deferred Expense (Income)	$ 13,000,000		$ 13,000,000				$ 12,000,000
Pledged Financial Instruments, Not Separately Reported, Loans Receivable, for Federal Home Loan Bank Debt	2,500,000,000		2,500,000,000			$ 2,000,000,000.0
Financing Receivable, Nonaccrual, Interest Income	0	$ 0	0	$ 0
Financing Receivable, Deferred Payments	8,000,000		8,000,000				37,000,000
Financing Receivable, Allowance for Credit Loss, Ending Balance	$ 8,000,000		$ 8,000,000				$ 37,000,000
Financing Receivable, Percent of Outstanding Loan Balance Deferred	0.21%		0.21%				1.24%
Financing Receivable, Modifications, Number of Contracts	0	0	0	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0	0	0	0
Mortgage Loans in Process of Foreclosure, Amount	$ 147,000		$ 147,000				$ 147,000
Commercial and Industrial Portfolio Segment [Member] | Term PPP Loans with Purchase Credit Deterioration [Member]
Loans and Leases Receivable, Allowance, Initial Allowance on Acquired Loans			813,000
Consumer Portfolio Segment [Member]
Financing Receivable, Overdraft Balance	450,000		450,000				536,000
Directors and Executive Officers [Member]
Loans and Leases Receivable, Related Parties, Ending Balance	$ 50,000,000		$ 50,000,000				$ 43,000,000
Kentucky Bancshares [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans, Gross					$ 755,175,000