Investments - Schedule of Investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,367	$ 3,709
Gross Unrealized Gains	21	2
Gross Unrealized Losses	129	212
Estimated Fair Value	4,259	3,499
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,781	2,303
Gross Unrealized Gains	16	2
Gross Unrealized Losses	65	121
Estimated Fair Value	2,732	2,184
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	951	787
Gross Unrealized Gains	4	0
Gross Unrealized Losses	44	56
Estimated Fair Value	911	731
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	376	308
Gross Unrealized Gains	1	0
Gross Unrealized Losses	12	20
Estimated Fair Value	365	288
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	172	160
Gross Unrealized Gains	0	0
Gross Unrealized Losses	6	11
Estimated Fair Value	166	149
U.S. Treasury notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	40	106
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	1
Estimated Fair Value	40	105
Other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	47	45
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2	3
Estimated Fair Value	$ 45	$ 42

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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