Fair Value Measurements (Schedule of assets, which are measured on a recurring basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Total fixed income securities	$ 241,587	$ 236,758
Total equity securities	49,805	47,561
Cash and cash equivalents	30,955	27,594	$ 18,148	$ 18,318
Total assets at fair value	322,347	311,913
U.S. Government and agencies [Member]
Total fixed income securities	15,287	9,649
Obligations of states and political subdivisions [Member]
Total fixed income securities	56,962	82,595
Corporate securities [Member]
Total fixed income securities	92,150	89,451
Residential mortgage-backed securities [Member]
Total fixed income securities	40,841	28,524
Commercial mortgage-backed securities [Member]
Total fixed income securities	14,582	11,170
Asset backed securities [Member]
Total fixed income securities	21,765	15,369
Basic materials [Member]
Total equity securities	1,263	892
Communications [Member]
Total equity securities	4,781	4,322
Consumer, cyclical [Member]
Total equity securities	9,149	9,339
Consumer, non-cyclical [Member]
Total equity securities	11,355	10,905
Energy [Member]
Total equity securities	2,054	2,231
Financial [Member]
Total equity securities	3,214	2,417
Industrial [Member]
Total equity securities	8,410	9,205
Technology [Member]
Total equity securities	9,579	8,250
Level I [Member]
Total fixed income securities
Total equity securities	49,805	47,561
Cash and cash equivalents	30,955	27,594
Total assets at fair value	80,760	75,155
Level I [Member] | U.S. Government and agencies [Member]
Total fixed income securities
Level I [Member] | Obligations of states and political subdivisions [Member]
Total fixed income securities
Level I [Member] | Corporate securities [Member]
Total fixed income securities
Level I [Member] | Residential mortgage-backed securities [Member]
Total fixed income securities
Level I [Member] | Commercial mortgage-backed securities [Member]
Total fixed income securities
Level I [Member] | Asset backed securities [Member]
Total fixed income securities
Level I [Member] | Basic materials [Member]
Total equity securities	1,263	892
Level I [Member] | Communications [Member]
Total equity securities	4,781	4,322
Level I [Member] | Consumer, cyclical [Member]
Total equity securities	9,149	9,339
Level I [Member] | Consumer, non-cyclical [Member]
Total equity securities	11,355	10,905
Level I [Member] | Energy [Member]
Total equity securities	2,054	2,231
Level I [Member] | Financial [Member]
Total equity securities	3,214	2,417
Level I [Member] | Industrial [Member]
Total equity securities	8,410	9,205
Level I [Member] | Technology [Member]
Total equity securities	9,579	8,250
Level II [Member]
Total fixed income securities	241,587	236,758
Total equity securities
Cash and cash equivalents
Total assets at fair value	241,587	236,758
Level II [Member] | U.S. Government and agencies [Member]
Total fixed income securities	15,287	9,649
Level II [Member] | Obligations of states and political subdivisions [Member]
Total fixed income securities	56,962	82,595
Level II [Member] | Corporate securities [Member]
Total fixed income securities	92,150	89,451
Level II [Member] | Residential mortgage-backed securities [Member]
Total fixed income securities	40,841	28,524
Level II [Member] | Commercial mortgage-backed securities [Member]
Total fixed income securities	14,582	11,170
Level II [Member] | Asset backed securities [Member]
Total fixed income securities	21,765	15,369
Level II [Member] | Basic materials [Member]
Total equity securities
Level II [Member] | Communications [Member]
Total equity securities
Level II [Member] | Consumer, cyclical [Member]
Total equity securities
Level II [Member] | Consumer, non-cyclical [Member]
Total equity securities
Level II [Member] | Energy [Member]
Total equity securities
Level II [Member] | Financial [Member]
Total equity securities
Level II [Member] | Industrial [Member]
Total equity securities
Level II [Member] | Technology [Member]
Total equity securities
Level III [Member]
Total fixed income securities
Total equity securities
Cash and cash equivalents
Total assets at fair value
Level III [Member] | U.S. Government and agencies [Member]
Total fixed income securities
Level III [Member] | Obligations of states and political subdivisions [Member]
Total fixed income securities
Level III [Member] | Corporate securities [Member]
Total fixed income securities
Level III [Member] | Residential mortgage-backed securities [Member]
Total fixed income securities
Level III [Member] | Commercial mortgage-backed securities [Member]
Total fixed income securities
Level III [Member] | Asset backed securities [Member]
Total fixed income securities
Level III [Member] | Basic materials [Member]
Total equity securities
Level III [Member] | Communications [Member]
Total equity securities
Level III [Member] | Consumer, cyclical [Member]
Total equity securities
Level III [Member] | Consumer, non-cyclical [Member]
Total equity securities
Level III [Member] | Energy [Member]
Total equity securities
Level III [Member] | Financial [Member]
Total equity securities
Level III [Member] | Industrial [Member]
Total equity securities
Level III [Member] | Technology [Member]
Total equity securities