Reinsurance (Voluntary Reinsurance) (Details) $ in Millions	Dec. 31, 2023 USD ($)
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	$ 4,823
A- to A++
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	4,047
B- to B++
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	769
Insolvent
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	$ 7