Investments, Fixed Maturities with Unrealized Losses (Details) $ in Thousands	Sep. 30, 2023 USD ($) Securities	Dec. 31, 2022 USD ($)
Debt Securities, Fair Value and Unrealized Losses by Fixed Maturities [Abstract]
Less than 12 months, fair value	$ 213,329	$ 794,302
Less than 12 months, unrealized losses	8,735	87,867
More than 12 months, fair value	905,227	238,021
More than 12 months, unrealized losses	$ 166,705	52,765
Number of fixed maturity securities classified as available for sale | Securities	931
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Debt Securities, Fair Value and Unrealized Losses by Fixed Maturities [Abstract]
Less than 12 months, fair value	$ 51,076	90,245
Less than 12 months, unrealized losses	1,224	5,327
More than 12 months, fair value	109,693	47,238
More than 12 months, unrealized losses	18,182	10,364
Obligations of States and Political Subdivisions [Member]
Debt Securities, Fair Value and Unrealized Losses by Fixed Maturities [Abstract]
Less than 12 months, fair value	38,870	261,465
Less than 12 months, unrealized losses	1,965	49,327
More than 12 months, fair value	281,436	47,945
More than 12 months, unrealized losses	79,938	16,493
Corporate Securities [Member]
Debt Securities, Fair Value and Unrealized Losses by Fixed Maturities [Abstract]
Less than 12 months, fair value	33,707	298,706
Less than 12 months, unrealized losses	2,325	22,272
More than 12 months, fair value	338,829	72,959
More than 12 months, unrealized losses	41,259	13,449
Mortgage-Backed Securities [Member]
Debt Securities, Fair Value and Unrealized Losses by Fixed Maturities [Abstract]
Less than 12 months, fair value	89,676	143,886
Less than 12 months, unrealized losses	3,221	10,941
More than 12 months, fair value	175,269	69,879
More than 12 months, unrealized losses	$ 27,326	$ 12,459