Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Undiscounted and Discounted Expected Gross Premiums and Expected Future Benefits and Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accident and health
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	$ 5,339	$ 4,919	$ 5,166
Expected future gross premiums, discounted	3,744	3,517	4,369
Expected future benefits and expenses, undiscounted	3,578	3,243	3,426
Expected future benefits and expenses, discounted	2,453	2,229	2,796
Traditional life
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	896	679	614
Expected future gross premiums, discounted	623	465	505
Expected future benefits and expenses, undiscounted	1,301	978	940
Expected future benefits and expenses, discounted	$ 657	$ 524	$ 673