Debt and Credit Facilities - Credit Facilities Narrative (Details)	Nov. 07, 2019 USD ($)	Dec. 31, 2023 USD ($)	Nov. 01, 2023 USD ($)	Oct. 31, 2023 USD ($)	Nov. 18, 2022 USD ($)	Sep. 08, 2022 USD ($)	Dec. 16, 2021 USD ($)	Jun. 21, 2019 USD ($)
Line of Credit Facility [Line Items]
Credit facilities outstanding		$ 1,581,365,000
Top Layer Reinsurance Ltd. | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		37,500,000
Top Layer Reinsurance Ltd. | Letter of Credit | Capital Support Agreement
Line of Credit Facility [Line Items]
Mandatory capital contribution in the event of capital and surplus reduction below a specified level		50,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facilities outstanding		0
Revolving Credit Facility | Medici
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		75,000,000
Credit facilities outstanding		$ 75,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Letter of credit aggregate commitment					$ 500,000,000
Line of credit facility, maximum borrowing capacity					700,000,000
Debt to capital ratio		0.35
Minimum net worth requirements		$ 4,000,000,000
Revolving Credit Facility | Bridge Loan
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity					$ 50,000,000
Secured Bilateral Facility | Letter of Credit | Wells Fargo
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity								$ 200,000,000
Credit facilities outstanding		175,000,000
Secured Bilateral Facility | Letter of Credit | Citibank Europe plc
Line of Credit Facility [Line Items]
Credit facilities outstanding		280,100,000
Secured Bilateral Facility | Letter of Credit | Citibank Europe plc | Bilateral Facility Participants
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 320,000,000	$ 180,000,000
Accordion feature, maximum borrowing capacity			$ 350,000,000
Loan agreement, remaining borrowing capacity		39,900,000
Unsecured Bilateral Facility | Letter of Credit | Wells Fargo
Line of Credit Facility [Line Items]
Credit facilities outstanding		0
Unsecured Bilateral Facility | Letter of Credit | Citibank Europe plc
Line of Credit Facility [Line Items]
Credit facilities outstanding		366,500,000
Unsecured Bilateral Facility | Letter of Credit | Credit Suisse (Switzerland) Ltd.
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity							$ 200,000,000
Credit facilities outstanding		193,300,000
Debt to capital ratio							0.35
Minimum net worth requirements							$ 4,000,000,000
Uncommitted Letter of Credit Facility | Letter of Credit | Société Générale, New York Branch (“SocGen”)
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity						$ 250,000,000
Credit facilities outstanding		250,000,000
Percentage of maximum aggregate amount to be secured						40.00%
Secured Letter of Credit Facility | Letter of Credit | Citibank Europe
Line of Credit Facility [Line Items]
Credit facilities outstanding		16,500,000
Renaissance Reinsurance FAL Facility | Bank of Montreal, Citibank Europe and ING Bank | Syndicate 1458
Line of Credit Facility [Line Items]
Aggregate amount of issuances	$ 140,000,000
Termination period from date of notice	4 years
Renaissance Reinsurance FAL Facility | Letter of Credit
Line of Credit Facility [Line Items]
Credit facilities outstanding		$ 225,000,000
Renaissance Reinsurance FAL Facility | Letter of Credit | Bank of Montreal, Citibank Europe and ING Bank | Syndicate 1458
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 225,000,000
Renaissance Reinsurance FAL Facility | Letter of Credit | Bank of Montreal, Citibank Europe and ING Bank | Syndicate 1458
Line of Credit Facility [Line Items]
Collateral amount, percent of aggregate outstanding letters of credit in case of Full Collateralization Event		100.00%
Renaissance Reinsurance FAL Facility | Letter of Credit | Bank of Montreal, Citibank Europe and ING Bank | Syndicate 1458 | Minimum
Line of Credit Facility [Line Items]
Collateral amount, percent of aggregate outstanding letters of credit	60.00%
Renaissance Reinsurance FAL Facility | Letter of Credit | Bank of Montreal, Citibank Europe and ING Bank | Syndicate 1458 | Maximum
Line of Credit Facility [Line Items]
Collateral amount, percent of aggregate outstanding letters of credit	100.00%