Summary of Significant Accounting Policies - Schedule of Impact of Adoption for Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Present value of expected future policy benefits
Pre-adoption balance				$ 1,501
Total adjustments		$ 51	$ (44)	(2)
Less: reinsurance recoverables				162
Post-adoption 1/1/2021 balance, after reinsurance recoverables				1,339
Amount in reserve	$ 3,110	2,753	3,469	3,206
As reported
Present value of expected future policy benefits
Pre-adoption balance				1,039
Effect of the remeasurement of the reserve at upper-medium grade fixed income-based rate
Present value of expected future policy benefits
Total adjustments				385
Adjustments for contracts with net premiums in excess of gross premiums
Present value of expected future policy benefits
Total adjustments				77
Revision of Prior Period, Adjustment
Present value of expected future policy benefits
Total adjustments				462
Accident and health
Present value of expected future policy benefits
Pre-adoption balance				1,037
Total adjustments		21	(44)	(2)
Less: reinsurance recoverables				159
Post-adoption 1/1/2021 balance, after reinsurance recoverables				878
Amount in reserve	2,453	2,229	2,796	2,577
Accident and health | As reported
Present value of expected future policy benefits
Pre-adoption balance				728
Accident and health | Effect of the remeasurement of the reserve at upper-medium grade fixed income-based rate
Present value of expected future policy benefits
Total adjustments				232
Less: reinsurance recoverables				33
Accident and health | Adjustments for contracts with net premiums in excess of gross premiums
Present value of expected future policy benefits
Total adjustments				77
Less: reinsurance recoverables				51
Accident and health | Revision of Prior Period, Adjustment
Present value of expected future policy benefits
Total adjustments				309
Traditional life
Present value of expected future policy benefits
Pre-adoption balance				464
Total adjustments		30	0	0
Less: reinsurance recoverables				3
Post-adoption 1/1/2021 balance, after reinsurance recoverables				461
Amount in reserve	$ 657	$ 524	$ 673	629
Traditional life | As reported
Present value of expected future policy benefits
Pre-adoption balance				311
Traditional life | Effect of the remeasurement of the reserve at upper-medium grade fixed income-based rate
Present value of expected future policy benefits
Total adjustments				153
Traditional life | Adjustments for contracts with net premiums in excess of gross premiums
Present value of expected future policy benefits
Total adjustments				0
Traditional life | Revision of Prior Period, Adjustment
Present value of expected future policy benefits
Total adjustments				153
Traditional Life Insurance Reclassified from Contractholder Funds
Present value of expected future policy benefits
Amount in reserve				$ 11