Investments - Summary of Investments (Detail) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 7,204	$ 6,205
Gross Unrealized Gains	51	13
Gross Unrealized Losses	(16)	(35)
Estimated Fair Value	7,239	6,183
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	297	349
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Estimated Fair Value	298	349
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,566	3,579
Gross Unrealized Gains	41	10
Gross Unrealized Losses	(1)	(13)
Estimated Fair Value	4,606	3,576
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	42	94
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	42	94
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,196	2,081
Gross Unrealized Gains	9	3
Gross Unrealized Losses	(1)	(6)
Estimated Fair Value	2,204	2,078
Mortgage-backed and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	103	102
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(14)	(16)
Estimated Fair Value	$ 89	$ 86

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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