Investments, Debt Securities by Contractual Maturity (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Amortized cost of debt securities, by contractual maturity [Abstract]
Due in one year or less	$ 5,383,493
Due after one year through five years	29,857,885
Due after five years through ten years	44,110,567
Due after ten years	86,533,317
Original or amortized cost	165,885,262	$ 170,595,860
Estimated fair value of debt securities, by contractual maturity [Abstract]
Due in one year or less	5,473,716
Due after one year through five years	41,316,685
Due after five years through ten years	48,479,332
Due after ten years	90,853,479
Estimated fair value	$ 186,123,212	$ 187,239,718	[1]

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