Fair Value Measurements and Investments - Additional Information (Detail) - USD ($)		3 Months Ended		6 Months Ended
	Feb. 01, 2024	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains (losses) on equity securities held as of the end of the period		$ (23,000,000)	$ (82,000,000)	$ 13,000,000	$ (184,000,000)
Impairment of indefinite-lived intangible assets and goodwill	$ 0
Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of debt		20,600,000,000		20,600,000,000		$ 20,500,000,000
Estimated Fair Value | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of debt		$ 18,600,000,000		$ 18,600,000,000		$ 17,700,000,000