Reinsurance - Narrative (Details) - USD ($) $ in Billions	Mar. 31, 2024	Dec. 31, 2023
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 71.1	$ 69.8
Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	90.00%	90.00%
Non-Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	9.00%	9.00%
Non-Investment Grade | Captive Insurers
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	82.00%	83.00%
Not Rated
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	1.00%	1.00%
Legacy Life And Retirement Run Off Lines Segment Member
Effects of Reinsurance [Line Items]
Ceded reserves	$ 26.9
Legacy General Insurance Run Off Lines Member
Effects of Reinsurance [Line Items]
Ceded reserves	$ 2.9
General Insurance | Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	49.00%	51.00%
Life and Retirement | Investment Grade
Effects of Reinsurance [Line Items]
Reinsurance recoverable (as a percent)	41.00%	39.00%