Business Restructuring Charges - Summary of Restructuring Accrual Activity (Detail) $ in Millions	6 Months Ended
	Mar. 31, 2021 USD ($)
CR Bard Inc
Restructuring Reserve [Roll Forward]
Balance at September 30, 2020	$ 16
Charged to expense	1
Cash payments	(5)
Non-cash settlements	0
Other adjustments	(1)
Balance at March 31, 2021	11
CR Bard Inc | Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2020	15
Charged to expense	0
Cash payments	(3)
Non-cash settlements	0
Other adjustments	(1)
Balance at March 31, 2021	11
CR Bard Inc | Other Restructuring
Restructuring Reserve [Roll Forward]
Balance at September 30, 2020	1
Charged to expense	1
Cash payments	(2)
Non-cash settlements	0
Other adjustments	0
Balance at March 31, 2021	0
Other Initiatives
Restructuring Reserve [Roll Forward]
Balance at September 30, 2020	20
Charged to expense	35
Cash payments	(33)
Non-cash settlements	(3)
Other adjustments	0
Balance at March 31, 2021	19
Other Initiatives | Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2020	17
Charged to expense	9
Cash payments	(13)
Non-cash settlements	0
Other adjustments	0
Balance at March 31, 2021	13
Other Initiatives | Other Restructuring
Restructuring Reserve [Roll Forward]
Balance at September 30, 2020	3
Charged to expense	26
Cash payments	(20)
Non-cash settlements	(3)
Other adjustments	0
Balance at March 31, 2021	$ 6