Schedule I - Summary of Investments-Other Than Investments in Related Parties (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Investments-Other Than Investments in Related Parties
Amortized Cost	$ 5,863,958
Fair Value	5,540,965
Amount at which shown in the Balance Sheet	5,540,965
Fixed maturities
Investments-Other Than Investments in Related Parties
Amortized Cost	4,658,169
Fair Value	4,335,008
Amount at which shown in the Balance Sheet	4,335,008
Fixed maturities \| United States Government and government agencies and authorities
Investments-Other Than Investments in Related Parties
Amortized Cost	1,459,742
Fair Value	1,340,313
Amount at which shown in the Balance Sheet	1,340,313
Fixed maturities \| States, municipalities and political subdivisions
Investments-Other Than Investments in Related Parties
Amortized Cost	585,047
Fair Value	547,258
Amount at which shown in the Balance Sheet	547,258
Fixed maturities \| Residential and commercial mortgage securities
Investments-Other Than Investments in Related Parties
Amortized Cost	571,163
Fair Value	517,940
Amount at which shown in the Balance Sheet	517,940
Fixed maturities \| Asset-backed securities
Investments-Other Than Investments in Related Parties
Amortized Cost	584,168
Fair Value	564,995
Amount at which shown in the Balance Sheet	564,995
Fixed maturities \| Foreign government and agency securities
Investments-Other Than Investments in Related Parties
Amortized Cost	77,516
Fair Value	67,447
Amount at which shown in the Balance Sheet	67,447
Fixed maturities \| All other corporate bonds
Investments-Other Than Investments in Related Parties
Amortized Cost	1,380,533
Fair Value	1,297,055
Amount at which shown in the Balance Sheet	1,297,055
Short-term investments
Investments-Other Than Investments in Related Parties
Amortized Cost	928,561
Fair Value	928,731
Amount at which shown in the Balance Sheet	928,731
Other invested assets
Investments-Other Than Investments in Related Parties
Amortized Cost	277,228
Fair Value	277,226
Amount at which shown in the Balance Sheet	$ 277,226

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 15
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 7
-Subparagraph (SX 210.12-15)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-7

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Amount of investment held by insurance company, excluding investment in related party.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 7
-Subparagraph (SX 210.12-15(Column D))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-7

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 7
-Subparagraph (SX 210.12-15(Column B))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-7

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 7
-Subparagraph (SX 210.12-15(Column C))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480032/946-320-S99-7

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