Summary of Investments - Fixed Maturities Unrealized Loss (Details) $ in Thousands	Jun. 30, 2024 USD ($) issue	Dec. 31, 2023 USD ($) issue
Number of Issues
Less than 12 months | issue	150	137
12 months or longer | issue	500	459
Fair Value
Less than 12 months	$ 474,675	$ 285,342
12 months or longer	1,025,212	960,788
Total	1,499,887	1,246,130
Gross Unrealized Loss
Less than 12 months	3,812	1,608
12 months or longer	97,936	89,740
Total	$ 101,748	$ 91,348
U.S. Treasury
Number of Issues
Less than 12 months | issue	2	2
12 months or longer | issue	8	6
Fair Value
Less than 12 months	$ 24,891	$ 4,138
12 months or longer	16,856	12,717
Total	41,747	16,855
Gross Unrealized Loss
Less than 12 months	47	46
12 months or longer	571	629
Total	$ 618	$ 675
U.S. government agency
Number of Issues
Less than 12 months | issue	4	3
12 months or longer | issue	23	23
Fair Value
Less than 12 months	$ 13,890	$ 10,986
12 months or longer	70,493	71,375
Total	84,383	82,361
Gross Unrealized Loss
Less than 12 months	91	14
12 months or longer	9,063	8,288
Total	$ 9,154	$ 8,302
General obligations | Midwest
Number of Issues
Less than 12 months | issue	7	11
12 months or longer | issue	7	3
Fair Value
Less than 12 months	$ 18,941	$ 19,534
12 months or longer	18,388	10,737
Total	37,329	30,271
Gross Unrealized Loss
Less than 12 months	123	61
12 months or longer	346	76
Total	$ 469	$ 137
General obligations | Northeast
Number of Issues
Less than 12 months | issue	9	3
12 months or longer | issue	1	1
Fair Value
Less than 12 months	$ 3,566	$ 5,371
12 months or longer	3,433	3,469
Total	6,999	8,840
Gross Unrealized Loss
Less than 12 months	64	8
12 months or longer	58	35
Total	$ 122	$ 43
General obligations | South
Number of Issues
Less than 12 months | issue	4	12
12 months or longer | issue	14	9
Fair Value
Less than 12 months	$ 8,914	$ 21,753
12 months or longer	26,042	16,610
Total	34,956	38,363
Gross Unrealized Loss
Less than 12 months	59	91
12 months or longer	709	309
Total	$ 768	$ 400
General obligations | West
Number of Issues
Less than 12 months | issue	6	17
12 months or longer | issue	12	7
Fair Value
Less than 12 months	$ 9,558	$ 38,204
12 months or longer	36,434	20,064
Total	45,992	58,268
Gross Unrealized Loss
Less than 12 months	46	140
12 months or longer	893	331
Total	$ 939	$ 471
Special revenue | Midwest
Number of Issues
Less than 12 months | issue	14	17
12 months or longer | issue	18	11
Fair Value
Less than 12 months	$ 23,903	$ 29,535
12 months or longer	33,974	23,375
Total	57,877	52,910
Gross Unrealized Loss
Less than 12 months	238	113
12 months or longer	491	245
Total	$ 729	$ 358
Special revenue | Northeast
Number of Issues
Less than 12 months | issue	3	6
12 months or longer | issue	13	8
Fair Value
Less than 12 months	$ 6,844	$ 15,131
12 months or longer	32,544	24,271
Total	39,388	39,402
Gross Unrealized Loss
Less than 12 months	28	67
12 months or longer	739	493
Total	$ 767	$ 560
Special revenue | South
Number of Issues
Less than 12 months | issue	13	21
12 months or longer | issue	42	32
Fair Value
Less than 12 months	$ 24,560	$ 45,639
12 months or longer	89,295	66,925
Total	113,855	112,564
Gross Unrealized Loss
Less than 12 months	213	232
12 months or longer	2,719	1,923
Total	$ 2,932	$ 2,155
Special revenue | West
Number of Issues
Less than 12 months | issue	14	20
12 months or longer | issue	30	16
Fair Value
Less than 12 months	$ 17,608	$ 32,789
12 months or longer	63,881	38,495
Total	81,489	71,284
Gross Unrealized Loss
Less than 12 months	207	248
12 months or longer	1,278	588
Total	$ 1,485	$ 836
Foreign bonds
Number of Issues
Less than 12 months | issue	0	0
12 months or longer | issue	5	9
Fair Value
Less than 12 months	$ 0	$ 0
12 months or longer	11,190	19,172
Total	11,190	19,172
Gross Unrealized Loss
Less than 12 months	0	0
12 months or longer	1,083	2,083
Total	$ 1,083	$ 2,083
Public utilities
Number of Issues
Less than 12 months | issue	5	4
12 months or longer | issue	48	48
Fair Value
Less than 12 months	$ 12,656	$ 7,151
12 months or longer	107,286	111,793
Total	119,942	118,944
Gross Unrealized Loss
Less than 12 months	148	74
12 months or longer	10,572	9,980
Total	$ 10,720	$ 10,054
Corporate bonds | Energy
Number of Issues
Less than 12 months | issue	3	0
12 months or longer | issue	13	15
Fair Value
Less than 12 months	$ 7,613	$ 0
12 months or longer	31,759	34,331
Total	39,372	34,331
Gross Unrealized Loss
Less than 12 months	52	0
12 months or longer	2,193	2,127
Total	$ 2,245	$ 2,127
Corporate bonds | Industrials
Number of Issues
Less than 12 months | issue	1	1
12 months or longer | issue	19	21
Fair Value
Less than 12 months	$ 2,931	$ 1,210
12 months or longer	40,660	47,462
Total	43,591	48,672
Gross Unrealized Loss
Less than 12 months	63	19
12 months or longer	4,948	4,920
Total	$ 5,011	$ 4,939
Corporate bonds | Consumer goods and services
Number of Issues
Less than 12 months | issue	6	4
12 months or longer | issue	29	28
Fair Value
Less than 12 months	$ 11,860	$ 14,724
12 months or longer	76,528	68,837
Total	88,388	83,561
Gross Unrealized Loss
Less than 12 months	155	98
12 months or longer	8,520	7,567
Total	$ 8,675	$ 7,665
Corporate bonds | Health care
Number of Issues
Less than 12 months | issue	3	1
12 months or longer | issue	9	11
Fair Value
Less than 12 months	$ 5,412	$ 3,000
12 months or longer	21,444	26,544
Total	26,856	29,544
Gross Unrealized Loss
Less than 12 months	95	2
12 months or longer	4,844	4,497
Total	$ 4,939	$ 4,499
Corporate bonds | Technology, media and telecommunications
Number of Issues
Less than 12 months | issue	4	1
12 months or longer | issue	27	27
Fair Value
Less than 12 months	$ 13,285	$ 3,969
12 months or longer	61,689	62,988
Total	74,974	66,957
Gross Unrealized Loss
Less than 12 months	344	35
12 months or longer	6,961	5,630
Total	$ 7,305	$ 5,665
Corporate bonds | Financial services
Number of Issues
Less than 12 months | issue	13	5
12 months or longer | issue	38	44
Fair Value
Less than 12 months	$ 69,749	$ 14,327
12 months or longer	100,662	112,517
Total	170,411	126,844
Gross Unrealized Loss
Less than 12 months	557	223
12 months or longer	5,822	7,158
Total	$ 6,379	$ 7,381
Mortgage-backed securities
Number of Issues
Less than 12 months | issue	18	3
12 months or longer | issue	50	48
Fair Value
Less than 12 months	$ 128,323	$ 2,783
12 months or longer	17,020	15,758
Total	145,343	18,541
Gross Unrealized Loss
Less than 12 months	777	33
12 months or longer	2,603	2,295
Total	$ 3,380	$ 2,328
Collateralized mortgage obligations | Government National Mortgage Association
Number of Issues
Less than 12 months | issue	11	2
12 months or longer | issue	41	40
Fair Value
Less than 12 months	$ 39,696	$ 7,055
12 months or longer	69,975	72,565
Total	109,671	79,620
Gross Unrealized Loss
Less than 12 months	304	27
12 months or longer	13,834	12,715
Total	$ 14,138	$ 12,742
Collateralized mortgage obligations | Federal Home Loan Mortgage Corporation
Number of Issues
Less than 12 months | issue	1	2
12 months or longer | issue	32	31
Fair Value
Less than 12 months	$ 2,528	$ 2,589
12 months or longer	62,781	66,361
Total	65,309	68,950
Gross Unrealized Loss
Less than 12 months	12	22
12 months or longer	14,490	13,155
Total	$ 14,502	$ 13,177
Collateralized mortgage obligations | Federal National Mortgage Association
Number of Issues
Less than 12 months | issue	3	2
12 months or longer | issue	20	20
Fair Value
Less than 12 months	$ 5,464	$ 5,454
12 months or longer	30,266	31,460
Total	35,730	36,914
Gross Unrealized Loss
Less than 12 months	74	55
12 months or longer	5,127	4,609
Total	$ 5,201	$ 4,664
Asset-backed securities
Number of Issues
Less than 12 months | issue	6	0
12 months or longer | issue	1	1
Fair Value
Less than 12 months	$ 22,483	$ 0
12 months or longer	2,612	2,962
Total	25,095	2,962
Gross Unrealized Loss
Less than 12 months	115	0
12 months or longer	72	87
Total	$ 187	$ 87