Credit Facilities (Narrative) (Details) - USD ($)			3 Months Ended		12 Months Ended
	May 26, 2016	Jun. 22, 2012	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	May 05, 2021	Feb. 23, 2021
Line of Credit Facility [Line Items]
Line of credit facility, commitment			$ 1,200,000
Uncommitted amount available			$ 340,000,000.0
Maximum percentage of admitted assets allowed for borrowing base			10.00%
Borrowings from FHLB			$ 519,000,000		$ 519,000,000
Wells Fargo Bank Group Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, term of credit facility	5 years	4 years
Line of credit facility, commitment	$ 800,000,000.0	$ 800,000,000.0	$ 13,319,000		$ 39,198,000
Wells Fargo Bank Group Credit Facility Tranche One [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 30, 2022		Dec. 30, 2022
Line of credit facility, commitment			$ 13,319,000		$ 39,198,000
Bermuda Re Wells Fargo Bank Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 30, 2022		Dec. 30, 2022
Line of credit facility, commitment			$ 500,000,000		$ 500,000,000	$ 500,000,000.0	$ 50,000,000.0
Bermuda Re Citibank LOC Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, commitment			$ 370,000,000		$ 370,000,000
Bermuda Re Citibank Letter of Credit Facility One [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 16, 2022		Feb. 28, 2022
Line of credit facility, commitment			$ 230,000,000		$ 230,000,000
Bermuda Re Citibank LOC Facility - Uncommitted [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 31, 2022		Dec. 31, 2022
Line of credit facility, commitment			$ 140,000,000		$ 140,000,000
Bermuda Re Bayerische Landesbank Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 31, 2022		Dec. 31, 2022
Line of credit facility, commitment			$ 200,000,000		$ 200,000,000
Bermuda Re Lloyd's Bank Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, commitment			$ 250,000,000.0		$ 50,000,000
Bermuda Re Lloyd's Bank Credit Facility One [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 31, 2022		Dec. 31, 2022
Line of credit facility, commitment			$ 50,000,000		$ 50,000,000
Bermuda Re Barclays Bilateral Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date			Dec. 31, 2022		Dec. 31, 2022
Line of credit facility, commitment			$ 200,000,000.0		$ 200,000,000
Federal Home Loan Bank Of New York [Member]
Line of Credit Facility [Line Items]
Admitted assets for FHLB			20,400,000
Maximum amount available under FHLB			2,000,000.0
Borrowings from FHLB			$ 519,000,000.0
Amount of borrowed funds required to be used to acquire additional membership stock, percentage			4.50%
Interest expense incurred			$ 700,000	$ 300,000
Federal Home Loan Bank Of New York [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
FHLB advance interest rate			0.53%
FHLB advance maturity			Nov. 30, 2021
Federal Home Loan Bank Of New York [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
FHLB advance interest rate			0.65%
FHLB advance maturity			Dec. 31, 2021