Investments -Schedule of Investments (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,214	$ 4,400
Gross Unrealized Gains	51	14
Gross Unrealized Losses	39	89
Estimated Fair Value	4,226	4,325
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,574	2,769
Gross Unrealized Gains	35	10
Gross Unrealized Losses	9	35
Estimated Fair Value	2,600	2,744
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	996	953
Gross Unrealized Gains	10	2
Gross Unrealized Losses	24	41
Estimated Fair Value	982	914
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	396	435
Gross Unrealized Gains	3	2
Gross Unrealized Losses	3	6
Estimated Fair Value	396	431
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	178	188
Gross Unrealized Gains	2	0
Gross Unrealized Losses	2	5
Estimated Fair Value	178	183
U.S. Treasury notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22	5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	22	5
Other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	48	50
Gross Unrealized Gains	1	0
Gross Unrealized Losses	1	2
Estimated Fair Value	$ 48	$ 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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