Reinsurance (Voluntary Reinsurance) (Details) $ in Millions	Dec. 31, 2021 USD ($)
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	$ 4,802
A- to A++
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	3,812
B- to B++
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	987
Insolvent
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	$ 3