Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value	$ 825		$ 825		$ 1,549
Remaining cash equivalents	2,900		2,900		1,300
Fair value of long-term debt	19,100		19,100		19,000
Fair value of debt reclassified from long term to short term					702
Asset Impairment Charges	34
Transfers of financial assets during the period.	364	$ 500	856	$ 1,316
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	$ 311		$ 311		$ 256
Life Sciences
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)		$ 39		$ 39
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