Note 2 - Investment Securities - Sales of Securities (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Proceeds from sales of securities	[1]	$ 8,415,795	$ 58,775,764	$ 21,969,870	$ 119,850,909
Pre-tax gross gains from sales of securities		6,312	4,281,828	65,880	4,815,373
Pre-tax gross losses from sales of securities		$ (69,900)	$ (30,055)	$ (91,004)	$ (187,090)

[1] Proceeds from sales of securities for the nine months ended September 30, 2016 includes $32.1 million receivable from the broker for the sale of securities