Business Restructuring Charges - Summary of Restructuring Accrual Activity (Detail) $ in Millions	6 Months Ended
	Mar. 31, 2019 USD ($)
CR Bard Inc
Restructuring Reserve [Roll Forward]
Balance at September 30, 2018	$ 33
Charged to expense	47
Cash payments	(24)
Non-cash settlements	(36)
Balance at March 31, 2019	20
CR Bard Inc | Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2018	33
Charged to expense	9
Cash payments	(22)
Non-cash settlements	0
Balance at March 31, 2019	20
CR Bard Inc | Other Restructuring
Restructuring Reserve [Roll Forward]
Balance at September 30, 2018	0
Charged to expense	38
Cash payments	(2)
Non-cash settlements	(36)
Balance at March 31, 2019	0
Other Initiatives
Restructuring Reserve [Roll Forward]
Balance at September 30, 2018	27
Charged to expense	25
Cash payments	(25)
Non-cash settlements	(4)
Balance at March 31, 2019	23
Other Initiatives | Employee Termination
Restructuring Reserve [Roll Forward]
Balance at September 30, 2018	23
Charged to expense	8
Cash payments	(11)
Non-cash settlements	0
Balance at March 31, 2019	20
Other Initiatives | Other Restructuring
Restructuring Reserve [Roll Forward]
Balance at September 30, 2018	4
Charged to expense	17
Cash payments	(14)
Non-cash settlements	(4)
Balance at March 31, 2019	$ 3