Investments - Schedule of Fair Value of Financial Instruments Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities
Available-for-sale Securities	$ 943,854	$ 943,623
U.S. Government and Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	93,429	98,975
Foreign Government
Schedule of Available-for-sale Securities
Available-for-sale Securities	4,023	3,982
States, Municipalities and Political Subdivisions
Schedule of Available-for-sale Securities
Available-for-sale Securities	139,040	144,468
Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	25,058	23,890
Corporate Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	295,243	301,988
Mortgage-backed securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	230,780	223,854
Asset-backed Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	62,734	64,037
Redeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	1,779	1,151
Fixed Maturities
Schedule of Available-for-sale Securities
Available-for-sale Securities	852,086	862,345
Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	2,260	1,759
Common Stock
Schedule of Available-for-sale Securities
Available-for-sale Securities	30,794	27,198
Nonredeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	1,681	2,005
Equity Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	91,468	80,978
Other Long-term Investments
Schedule of Available-for-sale Securities
Available-for-sale Securities	300	300
Mutual Fund
Schedule of Available-for-sale Securities
Available-for-sale Securities	56,733	50,016
Level 1
Schedule of Available-for-sale Securities
Available-for-sale Securities	89,188	79,275
Level 1 | U.S. Government and Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 1 | Foreign Government
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 1 | States, Municipalities and Political Subdivisions
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 1 | Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	86	0
Level 1 | Corporate Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 1 | Mortgage-backed securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 1 | Asset-backed Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 1 | Redeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	493	790
Level 1 | Fixed Maturities
Schedule of Available-for-sale Securities
Available-for-sale Securities	579	790
Level 1 | Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	2,260	1,759
Level 1 | Common Stock
Schedule of Available-for-sale Securities
Available-for-sale Securities	30,794	27,198
Level 1 | Nonredeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	1,681	2,005
Level 1 | Equity Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	88,309	78,185
Level 1 | Other Long-term Investments
Schedule of Available-for-sale Securities
Available-for-sale Securities	300	300
Level 1 | Mutual Fund
Schedule of Available-for-sale Securities
Available-for-sale Securities	53,574	47,223
Level 2
Schedule of Available-for-sale Securities
Available-for-sale Securities	854,666	864,348
Level 2 | U.S. Government and Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	93,429	98,975
Level 2 | Foreign Government
Schedule of Available-for-sale Securities
Available-for-sale Securities	4,023	3,982
Level 2 | States, Municipalities and Political Subdivisions
Schedule of Available-for-sale Securities
Available-for-sale Securities	139,040	144,468
Level 2 | Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	24,972	23,890
Level 2 | Corporate Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	295,243	301,988
Level 2 | Mortgage-backed securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	230,780	223,854
Level 2 | Asset-backed Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	62,734	64,037
Level 2 | Redeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	1,286	361
Level 2 | Fixed Maturities
Schedule of Available-for-sale Securities
Available-for-sale Securities	851,507	861,555
Level 2 | Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 2 | Common Stock
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 2 | Nonredeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 2 | Equity Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	3,159	2,793
Level 2 | Other Long-term Investments
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 2 | Mutual Fund
Schedule of Available-for-sale Securities
Available-for-sale Securities	3,159	2,793
Level 3
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | U.S. Government and Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Foreign Government
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | States, Municipalities and Political Subdivisions
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Corporate Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Mortgage-backed securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Asset-backed Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Redeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Fixed Maturities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Public Utilities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Common Stock
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Nonredeemable Preferred Stocks
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Equity Securities
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Other Long-term Investments
Schedule of Available-for-sale Securities
Available-for-sale Securities	0	0
Level 3 | Mutual Fund
Schedule of Available-for-sale Securities
Available-for-sale Securities	$ 0	$ 0