Note 10 - Income Taxes - Allocation of Income Tax Expense (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current		$ 2,943,000	$ 3,934,000	$ 4,730,000
Deferred income tax expense		1,790,000	18,000	10,000
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 1,560,000	1,560,000
Total income tax expense		$ 6,293,000	$ 3,952,000	$ 4,740,000