Note 3 - Available-for-sale Securities - Scheduled Maturities (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Due in one year or less, amortized cost	$ 10,079,265
Due in one year or less, fair value	10,083,100
Due after one to five years, amortized cost	30,524,131	27,151,751
Due after one to five years, fair value	31,550,267	27,510,536
Due after five to ten years, amortized cost	16,355,991	14,048,273
Due after five to ten years, fair value	16,811,943	14,163,270
Due after ten years, amortized cost	2,903,662	2,904,807
Due after ten years, fair value	2,929,490	2,843,372
Total, amortized cost	59,863,049	44,104,831
Total, fair value	$ 61,374,800	$ 44,517,178