Fair Value Measurements Fair Value Measurements - Fair Value Hierarchy (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	$ 782,556	$ 567,962
Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	45,820	39,598
Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	736,736	528,364
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	716,639	510,251
Fixed maturities [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	112	611
Fixed maturities [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	716,527	509,640
Fixed maturities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
U.S. Treasury securities and obligations of U.S. government agencies [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	112	611
U.S. Treasury securities and obligations of U.S. government agencies [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	112	611
U.S. Treasury securities and obligations of U.S. government agencies [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
U.S. Treasury securities and obligations of U.S. government agencies [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	153,635	154,600
Obligations of states, municipalities and political subdivisions [Member] | Level 1
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] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	153,635	154,600
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	182,364	96,752
Corporate and other securities [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Corporate and other securities [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	182,364	96,752
Corporate and other securities [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Commercial mortgage and asset-backed securities [Member]
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	193,906	149,867
Commercial mortgage and asset-backed securities [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Commercial mortgage and asset-backed securities [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	193,906	149,867
Commercial mortgage and asset-backed securities [Member] | 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	186,622	108,421
Residential mortgage-backed securities [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	0	0
Residential mortgage-backed securities [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value - available for sale	186,622	108,421
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	65,917	57,711
Equity securities [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	45,708	38,987
Equity securities [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	20,209	18,724
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	45,708	38,987
Exchange traded funds [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	45,708	38,987
Exchange traded funds [Member] | Level 2
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	20,209	18,724
Nonredeemable preferred stock [Member] | Level 1
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	0	0
Nonredeemable preferred stock [Member] | Level 2
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	20,209	18,724
Nonredeemable preferred stock [Member] | Level 3
Fair Value of Investments Measured on Recurring Basis [Line Items]
Fair value	$ 0	$ 0