Business Restructuring Charges - Summary of Restructuring Accrual Activity (Detail) $ in Millions	6 Months Ended
	Mar. 31, 2020 USD ($)
CR Bard Inc
Restructuring Reserve [Roll Forward]
Balance at September 30, 2019	$ 23
Charged to expense	29
Cash payments	(17)
Non-cash settlements	(16)
Balance at March 31, 2020	19
CR Bard Inc | Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2019	22
Charged to expense	6
Cash payments	(12)
Non-cash settlements	0
Balance at March 31, 2020	16
CR Bard Inc | Other Restructuring
Restructuring Reserve [Roll Forward]
Balance at September 30, 2019	1
Charged to expense	23
Cash payments	(5)
Non-cash settlements	(16)
Balance at March 31, 2020	3
Other Initiatives
Restructuring Reserve [Roll Forward]
Balance at September 30, 2019	34
Charged to expense	12
Cash payments	(35)
Non-cash settlements	(2)
Balance at March 31, 2020	9
Other Initiatives | Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2019	31
Charged to expense	(2)
Cash payments	(23)
Non-cash settlements	0
Balance at March 31, 2020	6
Other Initiatives | Other Restructuring
Restructuring Reserve [Roll Forward]
Balance at September 30, 2019	3
Charged to expense	14
Cash payments	(12)
Non-cash settlements	(2)
Balance at March 31, 2020	$ 3