Reinsurance (Voluntary Reinsurance) (Details) $ in Millions	Dec. 31, 2025 USD ($)
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	$ 5,840
A- to A++
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	4,864
B- to B++
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	967
Insolvent
Effects of Reinsurance [Line Items]
Total voluntary reinsurance outstanding balance	$ 9