Summary Of Investments Other Than Investments In Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	$ 6,061,318	$ 5,229,297
Fair Value	6,076,370	5,228,520
Amounts in the Balance Sheet	6,076,370	5,228,520
Fixed maturity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	4,982,458	4,394,983
Fair Value	4,913,378	4,319,336
Amounts in the Balance Sheet	4,913,378	4,319,336
U.S. government bonds and agencies
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	94,102	174,903
Fair Value	93,837	174,450
Amounts in the Balance Sheet	93,837	174,450
Municipal securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	3,018,428	2,797,971
Fair Value	2,987,054	2,777,258
Amounts in the Balance Sheet	2,987,054	2,777,258
Mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	271,444	201,727
Fair Value	259,421	186,887
Amounts in the Balance Sheet	259,421	186,887
Corporate securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	863,323	626,723
Fair Value	841,715	599,630
Amounts in the Balance Sheet	841,715	599,630
Collateralized loan obligations
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	623,817	486,984
Fair Value	626,255	484,947
Amounts in the Balance Sheet	626,255	484,947
Other asset-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	111,344	106,675
Fair Value	105,096	96,164
Amounts in the Balance Sheet	105,096	96,164
Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	795,068	654,939
Fair Value	879,175	730,693
Amounts in the Balance Sheet	879,175	730,693
Common stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	634,821	497,543
Fair Value	741,369	597,888
Amounts in the Balance Sheet	741,369	597,888
Non-redeemable preferred stock
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	52,206	64,860
Fair Value	42,603	51,563
Amounts in the Balance Sheet	42,603	51,563
Private equity funds measured at net asset value
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	108,041	92,536
Fair Value	95,203	81,242
Amounts in the Balance Sheet	95,203	81,242
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	283,792	179,375
Fair Value	283,817	178,491
Amounts in the Balance Sheet	$ 283,817	$ 178,491

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/1943274/2147477271/946-320-S99-7

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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/1943274/2147477271/946-320-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/1943274/2147477271/946-320-S99-7

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 7
-Subparagraph (SX 210.12-15(Column C))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-7

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