Schedule I (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 842,487
Investments	854,531	$ 528,647
Loans and Leases Receivable, Net Amount	20,000	0
US Government and Government Agencies and Authorities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	237,809	151,656
Available-for-sale Securities, Debt Securities	235,891	149,952
Foreign Government Debt Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,022	2,031
Available-for-sale Securities, Debt Securities	2,036	2,061
US States and Political Subdivisions Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	200,706	170,636
Available-for-sale Securities, Debt Securities	201,512	169,112
Public Utility, Bonds
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	20,215	7,687
Available-for-sale Securities, Debt Securities	20,257	7,730
Asset-backed Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	14,902
Available-for-sale Securities, Debt Securities	14,905
All Other Corporate Bonds
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	287,025	164,424
Available-for-sale Securities, Debt Securities	287,562	164,536
Redeemable Preferred Stock
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	755	1,182
Available-for-sale Securities, Debt Securities	692	1,125
Debt Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	763,434
Fixed Maturities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	763,434	497,616
Available-for-sale Securities, Debt Securities	762,855	494,516
Mutual Fund
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	29,079
Available-for-sale Securities, Equity Securities	31,924
Public Utility, Equities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	1,343	1,343
Available-for-sale Securities, Equity Securities	1,702	1,507
Other Common Stock
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	18,856	19,815
Available-for-sale Securities, Equity Securities	27,902	24,048
Common Stock
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Securities, Equity Securities	27,902
Nonredeemable Preferred Stock
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	1,718	2,916
Available-for-sale Securities, Equity Securities	1,767	2,843
Equity Securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	50,996	24,074
Available-for-sale Securities, Equity Securities	63,295	28,398
Other Long-term Investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Available-for-sale Securities, Amortized Cost Basis	8,057	5,493
Other Long-term Investments	$ 8,381	$ 5,733