Fair Value Measurements and Investments - Investment Income (Detail) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Interest and dividend income on cash and investments	$ 69	$ (16)	$ 80
Realized gains (losses), net on debt securities	0		4
Equity securities:
Unrealized gains (losses), net	(364)	721	115
Realized gains (losses), net	68	26	1
Investment income (expense)	$ (227)	$ 731	$ 200

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Amount of realized gain (loss) 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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Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on securities.

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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Amount of realized gain (loss) on investment.

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Amount of unrealized gain (loss) on investment.

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