Schedule I - Summary of Investments - Other than Investments in Related Parties (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Summary of investments - other than investments in related parties
Cost or Amortized Cost	$ 1,256,131
Estimated Fair Value	1,280,506
Amount at which shown in the Balance Sheet	1,280,506
Total fixed maturities
Summary of investments - other than investments in related parties
Cost or Amortized Cost	1,142,663
Estimated Fair Value	1,154,269
Amount at which shown in the Balance Sheet	1,154,269
U.S. government and government agencies and authorities
Summary of investments - other than investments in related parties
Cost or Amortized Cost	252,333
Estimated Fair Value	252,933
Amount at which shown in the Balance Sheet	252,933
Obligations of states and political subdivisions
Summary of investments - other than investments in related parties
Cost or Amortized Cost	382,811
Estimated Fair Value	390,433
Amount at which shown in the Balance Sheet	390,433
Corporate and other securities
Summary of investments - other than investments in related parties
Cost or Amortized Cost	507,519
Estimated Fair Value	510,903
Amount at which shown in the Balance Sheet	510,903
Total equity securities
Summary of investments - other than investments in related parties
Cost or Amortized Cost	92,326
Estimated Fair Value	105,095
Amount at which shown in the Balance Sheet	105,095
Industrial, miscellaneous and all other
Summary of investments - other than investments in related parties
Cost or Amortized Cost	92,326
Estimated Fair Value	105,095
Amount at which shown in the Balance Sheet	105,095
Other invested assets
Summary of investments - other than investments in related parties
Cost or Amortized Cost	21,142
Estimated Fair Value	21,142
Amount at which shown in the Balance Sheet	$ 21,142