Fair Value Measurements and Investments - Schedule of Debt Securities Classified by Contractual Maturity Date (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Due within one year	$ 1,789
Due after one year through five years	1,391
Total	$ 3,180	$ 5,451

Amount of 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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