Note 11 - Federal Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Tax at statutory rate (35%)	$ 16,410,000	$ 13,591,000	$ 8,819,000
Tax-exempt interest	(876,000)	(781,000)	(621,000)
Bank owned life insurance	(440,000)	(384,000)	(415,000)
Change in valuation allowance	(113,000)	(180,000)	0
Other	(7,000)	(435,000)	82,000
Tax expense	$ 14,974,000	$ 11,811,000	$ 7,865,000