Investments, Debt Securities by Contractual Maturity (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Amortized cost [Abstract]
Due in one year or less	$ 6,498,983
Due after one year through five years	51,055,408
Due after five years through ten years	50,690,937
Due after ten years	50,566,905
Original or amortized cost	158,812,233	$ 160,895,869
Estimated fair value [Abstract]
Due in one year or less	6,525,131
Due after one year through five years	53,028,854
Due after five years through ten years	53,501,649
Due after ten years	50,851,029
Estimated fair value	$ 163,906,663	$ 160,960,784	[1]

[1] Balance sheet audited at December 31, 2017.