Investments -Schedule of Investments (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,323	$ 4,400
Gross Unrealized Gains	38	14
Gross Unrealized Losses	51	89
Estimated Fair Value	4,310	4,325
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,630	2,769
Gross Unrealized Gains	28	10
Gross Unrealized Losses	15	35
Estimated Fair Value	2,643	2,744
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,003	953
Gross Unrealized Gains	6	2
Gross Unrealized Losses	29	41
Estimated Fair Value	980	914
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	425	435
Gross Unrealized Gains	2	2
Gross Unrealized Losses	3	6
Estimated Fair Value	424	431
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	197	188
Gross Unrealized Gains	2	0
Gross Unrealized Losses	3	5
Estimated Fair Value	196	183
U.S. Treasury notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20	5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	20	5
Other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	48	50
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1	2
Estimated Fair Value	$ 47	$ 48

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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