Fair Value Measurements and Investments (Tables)

6 Months Ended

Mar. 31, 2025

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

Assets and Liabilities Measured at Fair Value on a Recurring Basis

	Fair Value Measurements Using Inputs Considered as
	Level 1				Level 2
	March 31, 2025		September 30, 2024		March 31, 2025		September 30, 2024
	(in millions)
Assets
Cash equivalents and restricted cash equivalents:
Money market funds	$	9,438	$	10,403	$	—	$	—
U.S. Treasury securities	7		7		—		—
Investment securities:
Marketable equity securities	314		301		—		—
U.S. government-sponsored debt securities	—		—		305		496
U.S. Treasury securities	2,868		4,948		—		—
Other current and non-current assets:
Money market funds	27		25		—		—
Derivative instruments	—		—		194		103
Total	$	12,654	$	15,684	$	499	$	599
Liabilities
Accrued compensation and benefits:
Deferred compensation liability	$	235	$	238	$	—	$	—
Accrued and other liabilities:
Derivative instruments	—		—		252		226
Total	$	235	$	238	$	252	$	226

Schedule of Amortized Cost, Unrealized Gains and Losses, and Fair Value of Debt Securities

The amortized cost, unrealized gains and losses and fair value of debt securities were as follows:

	March 31, 2025
	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
	(in millions)
U.S. government-sponsored debt securities	$	303	$	2	$	—	$	305
U.S. Treasury securities	2,858		17		—		2,875
Total	$	3,161	$	19	$	—	$	3,180

	September 30, 2024
	Amortized Cost		Gross Unrealized				Fair Value
			Gains		Losses
	(in millions)
U.S. government-sponsored debt securities	$	492	$	4	$	—	$	496
U.S. Treasury securities	4,920		40		(5)		4,955
Total	$	5,412	$	44	$	(5)	$	5,451

Schedule of Debt Securities Classified by Contractual Maturity Date

The stated maturities of debt securities were as follows:

	March 31, 2025
	(in millions)
Due within one year	$	1,789
Due after one year through five years	1,391
Total	$	3,180

Schedule of Non-Marketable Equity Securities

The following table summarizes the Company’s non-marketable equity securities held as of period end that were accounted for using the fair value measurement alternative:

	March 31, 2025		September 30, 2024
	(in millions)
Initial cost basis	$	702	$	711
Adjustments:
Upward adjustments	850		910
Downward adjustments, including impairment	(494)		(465)
Carrying amount	$	1,058	$	1,156

Unrealized gains and losses of the Company’s non-marketable equity securities held as of period end that were accounted for using the fair value measurement alternative were as follows:

	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in millions)
Upward adjustments	$	7	$	—	$	7	$	9
Downward adjustments, including impairment	$	(31)	$	(15)	$	(49)	$	(15)