Note 10 - Federal Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Tax at statutory rate	$ 15,481,000	$ 11,518,000	$ 12,697,000
Tax-exempt interest	(658,000)	(681,000)	(644,000)
Bank owned life insurance	(233,000)	(238,000)	(804,000)
Change in valuation allowance	0	(94,000)	0
Other	105,000	205,000	(245,000)
Tax expense	$ 14,695,000	$ 10,710,000	$ 11,004,000