Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 1,549,000,000	$ 39,000,000
Remaining cash equivalents	1,276,000,000	497,000,000
Fair value of long-term debt	19,000,000,000.0	19,200,000,000
Fair value of debt classified from long term to short term	702,000,000	1,300,000,000
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	256,000,000
Transfers of financial assets during the period.	$ 2,200,000,000
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of short-term investments at the time of purchase	3 months
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of short-term investments at the time of purchase	1 year
Interventional
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)		$ 30,000,000
Medical
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Impairment Charges	$ 41,000,000		$ 58,000,000
Life Sciences
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	$ 57,000,000		$ 81,000,000