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Reinsurance (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reinsurance Disclosures [Line Items]
Percentage of ceded earned premiums to gross earned premiums	39.00%	38.00%	38.00%
Percentage of assumed earned premiums to net earned premiums	31.00%	30.00%	27.00%
Underwriting [Member]
Reinsurance Disclosures [Line Items]
Reinsurance recoverables	$ (1,496,265)	$ (834,648)	$ (893,230)
Reinsurance Recoverables, Gross	$ 4,000,000	$ 3,100,000
Underwriting [Member] | Ten Largest Reinsurers [Member]
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	65.00%	62.00%
Underwriting [Member] | RenaissanceRe
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	17.00%
Program services and other fronting [Member]
Reinsurance Disclosures [Line Items]
Reinsurance recoverables	$ 2,500,000	$ 3,000,000
Program Services [Member]
Reinsurance Disclosures [Line Items]
Reinsurance Recoverables, Gross	$ 4,900,000	$ 4,900,000
Program Services [Member] | Ten Largest Reinsurers [Member]
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	56.00%	67.00%
Program Services [Member] | Knight Insurance Company
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	10.00%
Other fronting | Nephila Reinsurers [Member]
Reinsurance Disclosures [Line Items]
Recoverable balances as a percentage of the total balance	100.00%

X

- Definition

The gross reinsurance recoverable balance of a specified reinsurer or reinsurers as a percentage of the total gross reinsurance recoverable balance at the end of the period.

+ References

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- Definition

Percentage of ceded premiums earned by the entity to gross premiums earned.

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- References

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Percentage of assumed premium earned to premium earned after effects of reinsurance, as disclosed in supplementary reinsurance information.

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

+ References

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- Definition

Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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