Investments by Category and Level (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
US Government and Government Agencies and Authorities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 235,891	$ 149,952
Foreign Government Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	2,036	2,061
US States and Political Subdivisions Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	201,512	169,112
Public Utility, Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	20,257	7,730
Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	287,562	164,536
Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	14,905
Redeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	692	1,125
Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	762,855	494,516
Mutual Fund
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	31,924
Public Utility, Equities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	1,702	1,507
Common Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	27,902	24,048
Nonredeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	1,767	2,843
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	63,295	28,398
Other Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	8,381	5,733
Level 1 | US Government and Government Agencies and Authorities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 1 | Foreign Government Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 1 | US States and Political Subdivisions Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 1 | Public Utility, Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 1 | Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 1 | Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0
Level 1 | Redeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	692	1,125
Level 1 | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	692	1,125
Level 1 | Mutual Fund
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	31,924
Level 1 | Public Utility, Equities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	1,702	1,507
Level 1 | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	27,902	24,048
Level 1 | Nonredeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	1,767	2,843
Level 1 | Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	63,295	28,398
Level 1 | Other Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	300	300
Level 2 | US Government and Government Agencies and Authorities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	235,891	149,952
Level 2 | Foreign Government Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	2,036	2,061
Level 2 | US States and Political Subdivisions Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	201,512	169,112
Level 2 | Public Utility, Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	20,257	7,730
Level 2 | Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	287,562	164,536
Level 2 | Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	14,905
Level 2 | Redeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 2 | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	762,163	493,391
Level 2 | Mutual Fund
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0
Level 2 | Public Utility, Equities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 2 | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 2 | Nonredeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 2 | Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 2 | Other Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	7,447	3,735
Level 3 | US Government and Government Agencies and Authorities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Foreign Government Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | US States and Political Subdivisions Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Public Utility, Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0
Level 3 | Redeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Mutual Fund
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0
Level 3 | Public Utility, Equities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Nonredeemable Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Level 3 | Other Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 634	$ 1,698