Undiscounted and Discounted Future Benefit Payments and Gross Premiums (Details) - Life policy reserves: - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Term Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	$ 4,816		$ 4,696
Undiscounted expected future gross premiums	4,386		4,470
Discounted expected future benefit payments	2,698	$ 2,751	2,691	$ 2,584
Discounted expected future gross premiums	2,601		2,674
Whole Life Insurance
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefit payments	1,660		1,586
Undiscounted expected future gross premiums	663		618
Discounted expected future benefit payments	637	$ 657	644	$ 614
Discounted expected future gross premiums	$ 402		$ 384