Reinsurance - Narrative (Details) - USD ($) $ in Billions	Sep. 30, 2023	Dec. 31, 2022
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 69.4	$ 71.8
Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	89.00%	92.00%
Non-Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	9.00%	7.00%
Non-Investment Grade | Captive Insurers
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	83.00%	77.00%
Not Rated
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	2.00%	1.00%
Legacy Life And Retirement Run Off Lines Segment Member
Effects of Reinsurance [Line Items]
Ceded reserves	$ 25.9
Legacy General Insurance Run Off Lines Member
Effects of Reinsurance [Line Items]
Ceded reserves	$ 3.0
General Insurance | Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	49.00%	53.00%
Life and Retirement | Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	40.00%	39.00%
Life and Retirement | Non-Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)		1.00%