Future Policy Benefits Reserves - Balances and Changes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Present value of future net premiums
Balance, January 1			$ 3,710	$ 3,993
Effect of changes in discount rate	$ 56	$ 154	(125)	(74)
Balance, January 1, at original locked in discount rate			3,585	3,919
Effect of changes in cash flow assumptions
Expect of actual variances from expected experience			(28)	(49)
Adjusted balance, January 1	3,497	3,811	3,557	3,870
Interest accrual	47	52
Net premiums: earned during period	(107)	(111)
Balance, end of period at original locked in discount rate	3,497	3,811
Effect of changes in discount rate	56	154	(125)	(74)
Balance, March 31	3,553	3,965
Present value of future benefits & expenses
Balance, January 1			17,669	17,472
Effect of changes in discount rate	78	704	(578)	(125)
Balance, January 1, at original locked in discount rate	17,091	17,347
Effect of changes in cash flow assumptions
Effect of actual variances from expected experience			(13)	(50)
Adjusted balance, January 1			17,078	17,297
Interest accrual	231	242
Benefit & expense payments	(321)	(302)
Balance, end of period at original locked in discount rate	16,988	17,237
Effect of changes in discount rate	78	704	(578)	$ (125)
Balance, March 31	17,066	17,941
Net LFPB	13,513	13,976	$ 13,959
Re-measurement loss of insurance claims and policyholders’ benefits	$ (15)	$ 1