Summary of Investments - Fair Value of Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fixed maturities:
Amortized Cost	$ 1,683,486	$ 1,771,041
Gross Unrealized Gain	1,926	6,810
Gross Unrealized Loss	96,163	91,347
Allowance for Credit Losses	1
Fair Value	1,589,248	1,686,503
U.S. Treasury
Fixed maturities:
Amortized Cost	51,211	51,211
Gross Unrealized Gain	101	325
Gross Unrealized Loss	714	675
Allowance for Credit Losses	0
Fair Value	50,598	50,861
U.S. government agency
Fixed maturities:
Amortized Cost	97,489	102,540
Gross Unrealized Gain	70	255
Gross Unrealized Loss	8,964	8,302
Allowance for Credit Losses	0
Fair Value	88,595	94,493
General obligations | Midwest
Fixed maturities:
Amortized Cost	48,181	52,712
Gross Unrealized Gain	114	132
Gross Unrealized Loss	307	137
Allowance for Credit Losses	0
Fair Value	47,988	52,707
General obligations | Northeast
Fixed maturities:
Amortized Cost	11,408	11,422
Gross Unrealized Gain	5	1
Gross Unrealized Loss	41	43
Allowance for Credit Losses	0
Fair Value	11,372	11,380
General obligations | South
Fixed maturities:
Amortized Cost	48,335	54,560
Gross Unrealized Gain	28	47
Gross Unrealized Loss	598	400
Allowance for Credit Losses	0
Fair Value	47,765	54,207
General obligations | West
Fixed maturities:
Amortized Cost	77,705	77,874
Gross Unrealized Gain	18	23
Gross Unrealized Loss	590	471
Allowance for Credit Losses	0
Fair Value	77,133	77,426
Special revenue | Midwest
Fixed maturities:
Amortized Cost	100,879	101,037
Gross Unrealized Gain	237	302
Gross Unrealized Loss	413	358
Allowance for Credit Losses	0
Fair Value	100,703	100,981
Special revenue | Northeast
Fixed maturities:
Amortized Cost	52,580	52,708
Gross Unrealized Gain	51	79
Gross Unrealized Loss	638	560
Allowance for Credit Losses	0
Fair Value	51,993	52,227
Special revenue | South
Fixed maturities:
Amortized Cost	164,309	166,119
Gross Unrealized Gain	167	302
Gross Unrealized Loss	2,638	2,155
Allowance for Credit Losses	0
Fair Value	161,838	164,266
Special revenue | West
Fixed maturities:
Amortized Cost	100,720	102,254
Gross Unrealized Gain	78	147
Gross Unrealized Loss	1,066	836
Allowance for Credit Losses	0
Fair Value	99,732	101,565
Foreign bonds
Fixed maturities:
Amortized Cost	13,269	21,255
Gross Unrealized Gain	0	0
Gross Unrealized Loss	1,093	2,083
Allowance for Credit Losses	0
Fair Value	12,176	19,172
Public utilities
Fixed maturities:
Amortized Cost	140,276	149,734
Gross Unrealized Gain	307	787
Gross Unrealized Loss	10,767	10,054
Allowance for Credit Losses	0
Fair Value	129,816	140,467
Corporate bonds | Energy
Fixed maturities:
Amortized Cost	41,901	45,351
Gross Unrealized Gain	79	249
Gross Unrealized Loss	2,220	2,127
Allowance for Credit Losses	0
Fair Value	39,760	43,473
Corporate bonds | Industrials
Fixed maturities:
Amortized Cost	59,656	74,760
Gross Unrealized Gain	181	727
Gross Unrealized Loss	4,919	4,939
Allowance for Credit Losses	0
Fair Value	54,918	70,548
Corporate bonds | Consumer goods and services
Fixed maturities:
Amortized Cost	89,135	103,315
Gross Unrealized Gain	0	271
Gross Unrealized Loss	8,225	7,665
Allowance for Credit Losses	0
Fair Value	80,910	95,921
Corporate bonds | Health care
Fixed maturities:
Amortized Cost	32,746	37,872
Gross Unrealized Gain	7	99
Gross Unrealized Loss	4,637	4,499
Allowance for Credit Losses	0
Fair Value	28,116	33,472
Corporate bonds | Technology, media and telecommunications
Fixed maturities:
Amortized Cost	82,329	87,002
Gross Unrealized Gain	111	451
Gross Unrealized Loss	6,715	5,665
Allowance for Credit Losses	0
Fair Value	75,725	81,788
Corporate bonds | Financial services
Fixed maturities:
Amortized Cost	123,031	152,329
Gross Unrealized Gain	39	743
Gross Unrealized Loss	6,298	7,380
Allowance for Credit Losses	1
Fair Value	116,771	145,691
Mortgage-backed securities
Fixed maturities:
Amortized Cost	55,865	23,800
Gross Unrealized Gain	0	11
Gross Unrealized Loss	2,668	2,328
Allowance for Credit Losses	0
Fair Value	53,197	21,483
Collateralized mortgage obligations | Government National Mortgage Association
Fixed maturities:
Amortized Cost	158,150	164,666
Gross Unrealized Gain	268	1,282
Gross Unrealized Loss	13,739	12,742
Allowance for Credit Losses	0
Fair Value	144,679	153,206
Collateralized mortgage obligations | Federal Home Loan Mortgage Corporation
Fixed maturities:
Amortized Cost	82,653	84,842
Gross Unrealized Gain	0	20
Gross Unrealized Loss	13,771	13,177
Allowance for Credit Losses	0
Fair Value	68,882	71,685
Collateralized mortgage obligations | Federal National Mortgage Association
Fixed maturities:
Amortized Cost	48,444	50,284
Gross Unrealized Gain	65	33
Gross Unrealized Loss	4,989	4,664
Allowance for Credit Losses	0
Fair Value	43,520	45,653
Asset-backed securities
Fixed maturities:
Amortized Cost	3,214	3,394
Gross Unrealized Gain	0	524
Gross Unrealized Loss	153	87
Allowance for Credit Losses	0
Fair Value	$ 3,061	$ 3,831