Fair Value Measurements and Investments - Additional Information (Detail) - USD ($)		3 Months Ended	9 Months Ended
	Feb. 01, 2020	Jun. 30, 2020	Jun. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1 and Level 2 assets		$ 0	$ 0
U.S. securities		3,100,000,000	3,100,000,000	$ 6,300,000,000
Upward adjustments		56,000,000	65,000,000
Downward adjustments		0	0
Impairment charges of non-marketable equity securities		6,000,000	6,000,000
Impairment of indefinite-lived intangible assets and goodwill	$ 0
Carrying value of long-term debt		$ 20,879,000,000	$ 20,879,000,000	16,729,000,000
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		$ 20,900,000,000	$ 20,900,000,000	16,700,000,000
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		$ 23,400,000,000	$ 23,400,000,000	$ 18,400,000,000