Credit Facilities (Summary Of Outstanding Letters Of Credit And Borrowings) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	May 05, 2021	Feb. 23, 2021	May 26, 2016	Jun. 22, 2012
Line of Credit Facility [Line Items]
Commitment	$ 1,200,000
Wells Fargo Bank Group Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment	13,319,000	$ 39,198,000			$ 800,000,000.0	$ 800,000,000.0
In Use	13,319,000	39,198,000
Wells Fargo Bank Group Credit Facility Tranche One [Member]
Line of Credit Facility [Line Items]
Commitment	13,319,000	39,198,000
In Use	$ 13,319,000	$ 39,198,000
Date of Expiry	Dec. 30, 2022	Dec. 30, 2022
Bermuda Re Wells Fargo Bank Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment	$ 500,000,000	$ 500,000,000	$ 500,000,000.0	$ 50,000,000.0
In Use	$ 422,521,000	$ 351,497,000
Date of Expiry	Dec. 30, 2022	Dec. 30, 2022
Bermuda Re Citibank LOC Facility [Member]
Line of Credit Facility [Line Items]
Commitment	$ 370,000,000	$ 370,000,000
In Use	333,600,000	333,429,000
Bermuda Re Citibank LOC Facility One [Member]
Line of Credit Facility [Line Items]
Commitment	230,000,000	230,000,000
In Use	$ 425,000	$ 4,425,000
Date of Expiry	Dec. 16, 2022	Feb. 28, 2022
Bermuda Re Citibank LOC Facility Two [Member]
Line of Credit Facility [Line Items]
In Use	$ 218,377,000	$ 925,000
Date of Expiry	Dec. 31, 2022	Mar. 01, 2022
Bermuda Re Citibank LOC Facility Three [Member]
Line of Credit Facility [Line Items]
In Use	$ 473,000	$ 1,264,000
Date of Expiry	Jan. 21, 2023	Nov. 24, 2022
Bermuda Re Citibank LOC Facility Four [Member]
Line of Credit Facility [Line Items]
In Use	$ 4,425,000	$ 423,000
Date of Expiry	Feb. 28, 2023	Dec. 16, 2022
Bermuda Re Citibank LOC Facility Five [Member]
Line of Credit Facility [Line Items]
In Use	$ 1,088,000	$ 146,000
Date of Expiry	Mar. 01, 2023	Dec. 20, 2022
Bermuda Re Citibank LOC Facility Six [Member]
Line of Credit Facility [Line Items]
In Use	$ 990,000	$ 216,622,000
Date of Expiry	Aug. 15, 2023	Dec. 31, 2022
Bermuda Re Citibank LOC Facility Seven [Member]
Line of Credit Facility [Line Items]
In Use	$ 1,240,000	$ 473,000
Date of Expiry	Sep. 23, 2023	Jan. 21, 2023
Bermuda Re Citibank LOC Facility Eight [Member]
Line of Credit Facility [Line Items]
In Use	$ 147,000	$ 985,000
Date of Expiry	Dec. 20, 2023	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	$ 140,000,000
In Use	$ 84,203,000	$ 84,203,000
Date of Expiry	Dec. 31, 2022	Dec. 31, 2022
Bermuda Re Citibank LOC Ten [Member]
Line of Credit Facility [Line Items]
In Use	$ 22,233,000	$ 22,731,000
Date of Expiry	Mar. 30, 2026	Dec. 30, 2025
Bermuda Re Bayerische Landesbank Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment	$ 200,000,000	$ 200,000,000
In Use	$ 156,197,000	$ 154,691,000
Date of Expiry	Dec. 31, 2022	Dec. 31, 2022
Bermuda Re Lloyd's Bank Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment	$ 250,000,000.0	$ 50,000,000
In Use	130,814,000	46,008,000
Bermuda Re Lloyd's Bank Credit Facility One [Member]
Line of Credit Facility [Line Items]
Commitment	50,000,000	50,000,000
In Use	$ 46,008,000	$ 46,008,000
Date of Expiry	Dec. 31, 2022	Dec. 31, 2022
Bermuda Re Lloyd's Bank Credit Facility - Uncommitted [Member]
Line of Credit Facility [Line Items]
Commitment	$ 200,000,000
In Use	$ 84,806,000
Date of Expiry	Dec. 31, 2022
Bermuda Re Barclays Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Commitment	$ 200,000,000.0	200,000,000
In Use	$ 171,628,000	$ 186,299,000
Date of Expiry	Dec. 31, 2022	Dec. 31, 2022