Note 10 - Federal Income Taxes - Consolidated Income Tax Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current expense	$ 14,945,000	$ 10,978,000	$ 10,170,000
Deferred expense	(4,141,000)	26,000	(372,000)
Change in valuation allowance	(94,000)	0	0
Tax expense	$ 10,710,000	$ 11,004,000	$ 9,798,000