Investments -Schedule of Investments (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,225	$ 3,988
Gross unrealized gains	2	52
Gross unrealized losses	127	32
Estimated Fair Value	4,100	4,008
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,459	2,437
Gross unrealized gains	2	35
Gross unrealized losses	61	7
Estimated Fair Value	2,400	2,465
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,000	963
Gross unrealized gains	0	11
Gross unrealized losses	54	21
Estimated Fair Value	946	953
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	397	363
Gross unrealized gains	0	3
Gross unrealized losses	6	2
Estimated Fair Value	391	364
U.S. Treasury notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	189	20
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated Fair Value	189	20
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	133	158
Gross unrealized gains	0	2
Gross unrealized losses	4	1
Estimated Fair Value	129	159
Other
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	47	47
Gross unrealized gains	0	1
Gross unrealized losses	2	1
Estimated Fair Value	$ 45	$ 47

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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