Fair Value - Financial Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Carrying Amount
Assets:
Other invested assets, primarily mortgage loans	$ 1,035	$ 1,040
Liabilities:
Short-term debt	1,083	853
Long-term debt	7,915	8,160
Estimated Fair Value
Assets:
Other invested assets, primarily mortgage loans	997	973
Liabilities:
Short-term debt	1,066	855
Long-term debt	7,640	7,621
Estimated Fair Value | Level 1
Assets:
Other invested assets, primarily mortgage loans
Liabilities:
Short-term debt
Long-term debt
Estimated Fair Value | Level 2
Assets:
Other invested assets, primarily mortgage loans
Liabilities:
Short-term debt	546	744
Long-term debt	7,255	7,035
Estimated Fair Value | Level 3
Assets:
Other invested assets, primarily mortgage loans	997	973
Liabilities:
Short-term debt	520	111
Long-term debt	$ 385	$ 586