Investments, Summary of Investments by Type (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Debt securities, at market [Abstract]
Debt securities, at market	$ 316,577	$ 284,099
Percent of debt securities at market to total investments (in hundredths)	86.50%	85.90%
Debt securities, at amortized cost [Abstract]
Debt securities, at amortized cost	$ 6,436	$ 7,417
Percent of debt securities at amortized cost to total investments (in hundredths)	1.76%	2.24%
Total debt securities	$ 323,014	$ 291,516
Percent of debt securities to total investments (in hundredths)	88.26%	88.14%
Equity securities, at market	$ 43,004	$ 39,247
Percentage of equity securities to total investments (in hundredths)	11.74%	11.86%
Total investments	$ 366,017	$ 330,763
Total investments (in hundredths)	100.00%	100.00%
United States Government Obligations and Authorities [Member]
Debt securities, at market [Abstract]
Debt securities, at market	$ 67,829	$ 62,323
Percent of debt securities at market to total investments (in hundredths)	18.53%	18.84%
Debt securities, at amortized cost [Abstract]
Debt securities, at amortized cost	$ 4,093	$ 4,490
Percent of debt securities at amortized cost to total investments (in hundredths)	1.12%	1.36%
Obligations of States and Political Subdivisions [Member]
Debt securities, at market [Abstract]
Debt securities, at market	$ 100,284	$ 91,614
Percent of debt securities at market to total investments (in hundredths)	27.40%	27.70%
Corporate [Member]
Debt securities, at market [Abstract]
Debt securities, at market	$ 136,553	$ 119,024
Percent of debt securities at market to total investments (in hundredths)	37.32%	35.99%
Debt securities, at amortized cost [Abstract]
Debt securities, at amortized cost	$ 2,219	$ 2,681
Percent of debt securities at amortized cost to total investments (in hundredths)	0.61%	0.81%
International [Member]
Debt securities, at market [Abstract]
Debt securities, at market	$ 11,911	$ 11,138
Percent of debt securities at market to total investments (in hundredths)	3.25%	3.37%
Debt securities, at amortized cost [Abstract]
Debt securities, at amortized cost	$ 125	$ 246
Percent of debt securities at amortized cost to total investments (in hundredths)	0.03%	0.07%