Note 2 - Available-for-sale Securities - Scheduled Maturities (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Due in one year or less, amortized cost	$ 400,000	$ 403,612
Due in one year or less, fair value	400,000	402,924
Due after one to five years, amortized cost	20,295,449	23,040,618
Due after one to five years, fair value	19,983,683	22,482,300
Due after five to ten years, amortized cost	12,052,696	10,515,614
Due after five to ten years, fair value	12,187,196	10,543,434
Total, amortized cost	32,748,145	33,959,844
Total, fair value	$ 32,570,879	$ 33,428,658