Investments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Investments related to 2012 contract conversion	$ 307	$ 331
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Weighted average duration of securities	5 years 10 months 24 days
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Weighted average duration of securities	5 years 4 months 24 days
Other asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Weighted average duration of securities	1 year