Investments, Debt Securities by Contractual Maturity (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Amortized cost of debt securities, by contractual maturity [Abstract]
Due in one year or less	$ 2,218,529
Due after one year through five years	35,657,891
Due after five years through ten years	44,894,902
Due after ten years	79,537,508
Original or amortized cost	162,308,830	$ 159,912,511
Estimated fair value of debt securities, by contractual maturity [Abstract]
Due in one year or less	2,255,623
Due after one year through five years	47,784,447
Due after five years through ten years	45,902,793
Due after ten years	78,633,896
Estimated fair value	$ 174,576,759	$ 178,555,225	[1]

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