Fair Value - Supplemental Information Regarding Available-for-Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 199	$ 201
Gross Unrealized Losses	(17)	(22)
Estimated Fair Value	182	179
Government
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	118	107
Gross Unrealized Losses	(10)	(11)
Estimated Fair Value	108	96
Corporate
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	65	69
Gross Unrealized Losses	(6)	(9)
Estimated Fair Value	59	60
Mortgage and Asset-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16	25
Gross Unrealized Losses	(1)	(2)
Estimated Fair Value	$ 15	$ 23