Unpaid Loss and Loss Adjustment Expenses Incurred loss & allocated loss adjustment expenses, net of reinsurance (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Supplementary Insurance Information, by Segment [Line Items]
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	$ 1,136,964
Accident Year 2007 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	1,039,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	39,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	190,128	$ 190,262	$ 190,144	$ 190,121	$ 190,575	$ 190,835	$ 188,375	$ 186,086	$ 178,901	$ 169,011
Accident Year 2008 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	6,267,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	34,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	185,508	185,558	185,723	185,966	186,685	186,769	184,989	184,499	$ 182,829
Accident Year 2009 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	29,795,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	35,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	174,053	174,202	174,598	174,915	175,753	176,234	173,657	$ 167,682
Accident Year 2010 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	17,971,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	25,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	101,900	101,876	102,280	102,695	104,898	106,744	$ 106,834
Accident Year 2011 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	(3,165,000)
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	24,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	65,453	65,025	64,666	63,739	63,131	$ 63,333
Accident Year 2012 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	25,640,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	34,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	70,336	70,168	69,661	70,801	$ 69,501
Accident Year 2013 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	351,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	32,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	79,409	78,463	76,676	$ 74,320
Accident Year 2014 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	1,695,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	34,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	83,145	79,818	$ 74,431
Accident Year 2015 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	5,326,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	35,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	97,647	$ 83,835
Accident Year 2016 [Member]
Supplementary Insurance Information, by Segment [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount	14,834,000
Liability for Unpaid Claims and Claims Adjustment Expense, Reported Claims, Amount	31,000
Supplementary Insurance Information, Benefits, Claims, Losses and Settlement Expense	$ 89,385