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Related Party Disclosures (Nephila) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party Transaction [Line Items]
Premiums ceded	$ 1,651,001	$ 1,465,604	$ 4,449,727	$ 3,879,411
Program services and other fronting [Member] | Nephila Reinsurers [Member]
Related Party Transaction [Line Items]
Gross premium volume	501,838	398,872	1,036,126	889,644
Premiums ceded	501,838	398,872	1,036,126	889,644
Underwriting [Member] | Nephila Reinsurers [Member]
Related Party Transaction [Line Items]
Premiums ceded	$ 10,058	$ 15,037	$ 39,905	$ 44,656

X

- Definition

Amount of written premiums ceded to other entities.

+ References

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-SubTopic 605
-Name Accounting Standards Codification
-Section 50
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- Definition

Amount of direct and assumed premiums written.

+ References

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-Topic 944
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(i))
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