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Reinsurance Reinsurance (Effect of Reinsurance and Retrocessional Reinsurance on Incurred Losses and Loss Adjustment Expenses) (Details) - Underwriting Operations [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Effects of Reinsurance [Line Items]
Gross losses and loss adjustment expenses	$ 6,970,871	$ 6,817,630	$ 5,281,424
Ceded losses and loss adjustment expenses	(1,917,318)	(1,496,265)	(834,648)
Net losses and loss adjustment expenses	$ 5,053,553	$ 5,321,365	$ 4,446,776

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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.

+ References

No definition available.

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- Definition

Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

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- Definition

Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-3

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

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