Investments - Schedule of Investments (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,400	$ 4,367
Gross Unrealized Gains	14	21
Gross Unrealized Losses	89	129
Estimated Fair Value	4,325	4,259
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,769	2,781
Gross Unrealized Gains	10	16
Gross Unrealized Losses	35	65
Estimated Fair Value	2,744	2,732
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	953	951
Gross Unrealized Gains	2	4
Gross Unrealized Losses	41	44
Estimated Fair Value	914	911
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	435	376
Gross Unrealized Gains	2	1
Gross Unrealized Losses	6	12
Estimated Fair Value	431	365
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	188	172
Gross Unrealized Gains	0	0
Gross Unrealized Losses	5	6
Estimated Fair Value	183	166
U.S. Treasury notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5	40
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	5	40
Other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	50	47
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2	2
Estimated Fair Value	$ 48	$ 45

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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