Credit Facilities (Summary Of Outstanding Letters Of Credit And Borrowings) (Details) £ in Thousands	12 Months Ended
	Dec. 31, 2021 GBP (£)	Dec. 31, 2020 GBP (£)	Dec. 31, 2021 USD ($)	May 05, 2021 USD ($)	Feb. 23, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 25, 2020 USD ($)	Dec. 31, 2019 USD ($)	May 26, 2016 USD ($)	Jun. 22, 2012 USD ($)
Line of Credit Facility [Line Items]
Commitment			$ 1,200,000,000
Wells Fargo Bank Group Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment			39,198,000			$ 800,000,000			$ 800,000,000.0	$ 800,000,000.0
In Use			39,198,000			753,932,000
Wells Fargo Bank Group Credit Facility Tranche One [Member]
Line of Credit Facility [Line Items]
In Use							$ 50,000,000.0	$ 0
Wells Fargo Bank Group Credit Facility Tranche One [Member] \| Debt Instrument Redemption Period One [Member]
Line of Credit Facility [Line Items]
Commitment			39,198,000			200,000,000
In Use			39,198,000			164,242,000
Date of Expiry	Dec. 30, 2022	Dec. 31, 2021
Wells Fargo Bank Group Credit Facility Tranche Two [Member] \| Debt Instrument Redemption Period One [Member]
Line of Credit Facility [Line Items]
Commitment						600,000,000
In Use						589,690,000
Date of Expiry		Dec. 31, 2021
Bermuda Re Wells Fargo Bank Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment			500,000,000	$ 500,000,000.0	$ 50,000,000.0
In Use			351,497,000
Date of Expiry	Dec. 30, 2022
Bermuda Re Citibank LOC Facility [Member]
Line of Credit Facility [Line Items]
Commitment			370,000,000			200,000,000
In Use			333,429,000			185,483,000
Bermuda Re Citibank LOC Facility One [Member]
Line of Credit Facility [Line Items]
Commitment			230,000,000			200,000,000
In Use			4,425,000			4,425,000
Date of Expiry	Feb. 28, 2022	Feb. 28, 2021
Bermuda Re Citibank LOC Facility Two [Member]
Line of Credit Facility [Line Items]
In Use			925,000			3,672,000
Date of Expiry	Mar. 01, 2022	Nov. 24, 2021
Bermuda Re Citibank LOC Facility Three [Member]
Line of Credit Facility [Line Items]
In Use			1,264,000			448,000
Date of Expiry	Nov. 24, 2022	Dec. 16, 2021
Bermuda Re Citibank LOC Facility Four [Member]
Line of Credit Facility [Line Items]
In Use			423,000			115,000
Date of Expiry	Dec. 16, 2022	Dec. 20, 2021
Bermuda Re Citibank LOC Facility Five [Member]
Line of Credit Facility [Line Items]
In Use			146,000			136,383,000
Date of Expiry	Dec. 20, 2022	Dec. 31, 2021
Bermuda Re Citibank LOC Facility Six [Member]
Line of Credit Facility [Line Items]
In Use			216,622,000			39,619,000
Date of Expiry	Dec. 31, 2022	Dec. 30, 2024
Bermuda Re Citibank LOC Facility Seven [Member]
Line of Credit Facility [Line Items]
In Use			473,000			$ 821,000
Date of Expiry	Jan. 21, 2023	Aug. 15, 2022
Bermuda Re Citibank LOC Facility Eight [Member]
Line of Credit Facility [Line Items]
In Use			985,000
Date of Expiry	Aug. 15, 2023
Bermuda Re Citibank LOC Facility Nine [Member]
Line of Credit Facility [Line Items]
In Use			1,234,000
Date of Expiry	Sep. 23, 2023
Bermuda Re Citibank LOC Facility - Uncommitted [Member]
Line of Credit Facility [Line Items]
Commitment			140,000,000
In Use			84,203,000
Date of Expiry	Dec. 31, 2022
Bermuda Re Citibank LOC Ten [Member]
Line of Credit Facility [Line Items]
In Use			22,731,000
Date of Expiry	Dec. 30, 2025
Everest International Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment \| £		£ 52,175
In Use \| £		£ 52,175
Date of Expiry		Dec. 31, 2024
Bermuda Re Bayerische Landesbank Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment			200,000,000.0
In Use			154,691,000
Date of Expiry	Dec. 31, 2022
Bermuda Re Lloyd's Bank Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment			50,000,000
In Use			46,008,000
Date of Expiry	Dec. 31, 2022
Bermuda Re Barclays Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment			200,000,000
In Use			$ 186,299,000
Date of Expiry	Dec. 31, 2022