Fair Value Measurements and Investments - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Feb. 01, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. securities		$ 1,800,000,000		$ 1,800,000,000		$ 3,800,000,000
Impairment of indefinite-lived intangible assets and goodwill	$ 0
Carrying value of long-term debt		20,996,000,000		20,996,000,000		24,070,000,000
Unrealized gain on equity securities held as of the end of the period		$ 434,000,000	$ 68,000,000	$ 610,000,000	$ 59,000,000
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, stated maturities		1 year		1 year
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, stated maturities		5 years		5 years
Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of long-term debt		$ 21,000,000,000.0		$ 21,000,000,000.0		24,100,000,000
Estimated Fair Value | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of long-term debt		$ 22,900,000,000		$ 22,900,000,000		$ 26,600,000,000