Note 11 - Federal Income Taxes - Consolidated Income Tax Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current expense	$ 10,978,000	$ 10,170,000	$ 13,978,000
Deferred expense	26,000	(372,000)	(505,000)
Effect of federal tax law change	0	0	1,336,000
Federal income tax benefit	$ 11,004,000	$ 9,798,000	$ 14,809,000