Investments, Debt Securities by Contractual Maturity (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Amortized cost of debt securities, by contractual maturity [Abstract]
Due in one year or less	$ 1,218,125
Due after one year through five years	36,349,018
Due after five years through ten years	43,553,027
Due after ten years	83,770,893
Original or amortized cost	164,891,063	$ 159,912,511
Estimated fair value of debt securities, by contractual maturity [Abstract]
Due in one year or less	1,239,718
Due after one year through five years	47,511,317
Due after five years through ten years	45,272,788
Due after ten years	85,180,490
Estimated fair value	$ 179,204,313	$ 178,555,225	[1]

[1] Balance sheet audited at December 31, 2016.