Summary of Investments - Fair Value of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fixed maturities:
Amortized Cost	$ 1,681,117	$ 1,662,680
Gross Unrealized Appreciation	1,460	2,784
Gross Unrealized Depreciation	114,194	114,125
Fair Value	1,568,383	1,551,339
Allowance for Credit Losses	1	3
Carrying Value	1,568,382	1,551,336
U.S. Treasury
Fixed maturities:
Amortized Cost	22,609	15,684
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	1,045	1,009
Fair Value	21,564	14,675
Allowance for Credit Losses	0	0
Carrying Value	21,564	14,675
U.S. government agency
Fixed maturities:
Amortized Cost	90,766	94,092
Gross Unrealized Appreciation	0	35
Gross Unrealized Depreciation	9,521	9,721
Fair Value	81,245	84,406
Allowance for Credit Losses	0	0
Carrying Value	81,245	84,406
General obligations \| Midwest
Fixed maturities:
Amortized Cost	58,779	61,191
Gross Unrealized Appreciation	115	185
Gross Unrealized Depreciation	411	263
Fair Value	58,483	61,113
Allowance for Credit Losses	0	0
Carrying Value	58,483	61,113
General obligations \| Northeast
Fixed maturities:
Amortized Cost	11,458	15,518
Gross Unrealized Appreciation	0	18
Gross Unrealized Depreciation	60	73
Fair Value	11,398	15,463
Allowance for Credit Losses	0	0
Carrying Value	11,398	15,463
General obligations \| South
Fixed maturities:
Amortized Cost	55,446	64,851
Gross Unrealized Appreciation	24	57
Gross Unrealized Depreciation	709	927
Fair Value	54,761	63,981
Allowance for Credit Losses	0	0
Carrying Value	54,761	63,981
General obligations \| West
Fixed maturities:
Amortized Cost	83,761	87,094
Gross Unrealized Appreciation	68	163
Gross Unrealized Depreciation	795	712
Fair Value	83,034	86,545
Allowance for Credit Losses	0	0
Carrying Value	83,034	86,545
Special revenue \| Midwest
Fixed maturities:
Amortized Cost	102,770	103,107
Gross Unrealized Appreciation	172	224
Gross Unrealized Depreciation	809	1,065
Fair Value	102,133	102,266
Allowance for Credit Losses	0	0
Carrying Value	102,133	102,266
Special revenue \| Northeast
Fixed maturities:
Amortized Cost	52,962	55,292
Gross Unrealized Appreciation	73	76
Gross Unrealized Depreciation	1,082	1,148
Fair Value	51,953	54,220
Allowance for Credit Losses	0	0
Carrying Value	51,953	54,220
Special revenue \| South
Fixed maturities:
Amortized Cost	168,751	184,108
Gross Unrealized Appreciation	68	278
Gross Unrealized Depreciation	3,253	3,529
Fair Value	165,566	180,857
Allowance for Credit Losses	0	0
Carrying Value	165,566	180,857
Special revenue \| West
Fixed maturities:
Amortized Cost	105,781	113,594
Gross Unrealized Appreciation	81	275
Gross Unrealized Depreciation	1,549	1,657
Fair Value	104,313	112,212
Allowance for Credit Losses	0	0
Carrying Value	104,313	112,212
Foreign bonds
Fixed maturities:
Amortized Cost	41,128	36,129
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	4,355	4,480
Fair Value	36,773	31,649
Allowance for Credit Losses	0	0
Carrying Value	36,773	31,649
Public utilities
Fixed maturities:
Amortized Cost	141,667	138,752
Gross Unrealized Appreciation	55	65
Gross Unrealized Depreciation	13,418	13,406
Fair Value	128,304	125,411
Allowance for Credit Losses	0	0
Carrying Value	128,304	125,411
Corporate bonds \| Energy
Fixed maturities:
Amortized Cost	44,448	36,507
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	3,105	3,298
Fair Value	41,343	33,209
Allowance for Credit Losses	0	0
Carrying Value	41,343	33,209
Corporate bonds \| Industrials
Fixed maturities:
Amortized Cost	63,748	58,334
Gross Unrealized Appreciation	135	62
Gross Unrealized Depreciation	5,270	5,554
Fair Value	58,613	52,842
Allowance for Credit Losses	0	0
Carrying Value	58,613	52,842
Corporate bonds \| Consumer goods and services
Fixed maturities:
Amortized Cost	100,369	100,539
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	9,847	10,598
Fair Value	90,522	89,941
Allowance for Credit Losses	0	0
Carrying Value	90,522	89,941
Corporate bonds \| Health care
Fixed maturities:
Amortized Cost	37,932	32,987
Gross Unrealized Appreciation	26	24
Gross Unrealized Depreciation	5,145	5,419
Fair Value	32,813	27,592
Allowance for Credit Losses	0	0
Carrying Value	32,813	27,592
Corporate bonds \| Technology, media and telecommunications
Fixed maturities:
Amortized Cost	72,097	67,193
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	6,732	7,253
Fair Value	65,365	59,940
Allowance for Credit Losses	0	0
Carrying Value	65,365	59,940
Corporate bonds \| Financial services
Fixed maturities:
Amortized Cost	137,047	132,849
Gross Unrealized Appreciation	112	851
Gross Unrealized Depreciation	10,766	9,408
Fair Value	126,393	124,292
Allowance for Credit Losses	1	3
Carrying Value	126,392	124,289
Mortgage-backed securities
Fixed maturities:
Amortized Cost	25,339	20,450
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	2,666	2,750
Fair Value	22,673	17,700
Allowance for Credit Losses	0	0
Carrying Value	22,673	17,700
Collateralized mortgage obligations \| Government national mortgage association
Fixed maturities:
Amortized Cost	114,875	97,839
Gross Unrealized Appreciation	15	0
Gross Unrealized Depreciation	14,369	13,291
Fair Value	100,521	84,548
Allowance for Credit Losses	0	0
Carrying Value	100,521	84,548
Collateralized mortgage obligations \| Federal home loan mortgage corporation
Fixed maturities:
Amortized Cost	91,108	92,366
Gross Unrealized Appreciation	0	0
Gross Unrealized Depreciation	13,948	13,528
Fair Value	77,160	78,838
Allowance for Credit Losses	0	0
Carrying Value	77,160	78,838
Collateralized mortgage obligations \| Federal national mortgage association
Fixed maturities:
Amortized Cost	54,521	50,272
Gross Unrealized Appreciation	18	5
Gross Unrealized Depreciation	5,213	4,891
Fair Value	49,326	45,386
Allowance for Credit Losses	0	0
Carrying Value	49,326	45,386
Asset-backed securities
Fixed maturities:
Amortized Cost	3,755	3,932
Gross Unrealized Appreciation	498	466
Gross Unrealized Depreciation	126	145
Fair Value	4,127	4,253
Allowance for Credit Losses	0	0
Carrying Value	$ 4,127	$ 4,253

Debt Securities, Available-for-Sale, Excluding Accrued Interest, Before Allowance For Credit Loss

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- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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- Definition

Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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- Definition

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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