Note 4 - Fair Value: Fair Value Measurements, by Fair Value hierarchy (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Corporate Debt Securities
Investments, Fair Value Disclosure	$ 432,375	$ 391,113
US States and Political Subdivisions Debt Securities
Investments, Fair Value Disclosure	242,195,833	220,663,305
Investments, Fair Value Disclosure	242,628,208	221,054,418
Fair Value, Inputs, Level 1 | Corporate Debt Securities
Investments, Fair Value Disclosure	432,375	391,113
Fair Value, Inputs, Level 1 | US States and Political Subdivisions Debt Securities
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1
Investments, Fair Value Disclosure	432,375	391,113
Fair Value, Inputs, Level 2 | Corporate Debt Securities
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 | US States and Political Subdivisions Debt Securities
Investments, Fair Value Disclosure	242,195,833	220,663,305
Fair Value, Inputs, Level 2
Investments, Fair Value Disclosure	242,195,833	220,663,305
Fair Value, Inputs, Level 3 | Corporate Debt Securities
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 | US States and Political Subdivisions Debt Securities
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3
Investments, Fair Value Disclosure	$ 0	$ 0