Note 6 - Fair Value Measurements - Schedule of Fair Value Reported on a Recurring Basis (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Securities	$ 543,102	$ 454,058
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Available-for-Sale Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Domestic Equities [Member]
Equity Securities	337,010	259,843
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | International Equities [Member]
Equity Securities	193,672	179,083
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other [Member]
Equity Securities	12,420	15,132
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Available-for-Sale Securities	19,702,622	16,249,414
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Domestic Equities [Member]
Equity Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | International Equities [Member]
Equity Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other [Member]
Equity Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Available-for-Sale Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Domestic Equities [Member]
Equity Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | International Equities [Member]
Equity Securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other [Member]
Equity Securities