Fair Value Measurements - Fair Value Hierarchy (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	$ 1,239,799	$ 1,211,462
Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	106,014	98,050
Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	1,133,785	1,113,412
Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	0	0
Fixed maturities [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	1,099,763	1,081,800
Fixed maturities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Fixed maturities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	1,099,763	1,081,800
Fixed maturities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Obligations of states, municipalities and political subdivisions [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	214,363	230,906
Obligations of states, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Obligations of states, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	214,363	230,906
Obligations of states, municipalities and political subdivisions [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Corporate and other securities [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	342,826	316,608
Corporate and other securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Corporate and other securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	342,826	316,608
Corporate and other securities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Asset-backed securities [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	259,425	240,661
Asset-backed securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Asset-backed securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	259,425	240,661
Asset-backed securities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Commercial mortgage-backed securities
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	64,826	70,969
Commercial mortgage-backed securities | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Commercial mortgage-backed securities | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	64,826	70,969
Commercial mortgage-backed securities | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Residential mortgage-backed securities [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	218,323	222,656
Residential mortgage-backed securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Residential mortgage-backed securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	218,323	222,656
Residential mortgage-backed securities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Equity securities [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	140,036	129,662
Equity securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	106,014	98,050
Equity securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	34,022	31,612
Equity securities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	0	0
Exchange traded funds [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	106,014	98,050
Exchange traded funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	106,014	98,050
Exchange traded funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	0	0
Exchange traded funds [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	0	0
Nonredeemable preferred stock [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	34,022	31,612
Nonredeemable preferred stock [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	0	0
Nonredeemable preferred stock [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	34,022	31,612
Nonredeemable preferred stock [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	$ 0	$ 0