Business Restructuring Charges - Changes in Restructuring Balance (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
CR Bard Inc
Restructuring Reserve [Roll Forward]
Beginning balance	$ 23	$ 33	$ 0
Charged to expense	49	118	292
Cash payments	(32)	(39)	(106)
Non-cash settlements	(24)	(89)	(153)
Ending balance	16	23	33
CR Bard Inc | Employee Termination
Restructuring Reserve [Roll Forward]
Beginning balance	22	33	0
Charged to expense	7	23	136
Cash payments	(14)	(34)	(103)
Non-cash settlements	0	0	0
Ending balance	15	22	33
CR Bard Inc | Other
Restructuring Reserve [Roll Forward]
Beginning balance	1	0	0
Charged to expense	42	95	156
Cash payments	(18)	(5)	(3)
Non-cash settlements	(24)	(89)	(153)
Ending balance	1	1	0
Other Initiatives
Restructuring Reserve [Roll Forward]
Beginning balance	34	27	55
Charged to expense	46	62	52
Cash payments	(58)	(52)	(79)
Non-cash settlements	(2)	(3)	(1)
Ending balance	20	34	27
Other Initiatives | Employee Termination
Restructuring Reserve [Roll Forward]
Beginning balance	31	23	49
Charged to expense	13	29	30
Cash payments	(27)	(21)	(56)
Non-cash settlements	0	0	0
Ending balance	17	31	23
Other Initiatives | Other
Restructuring Reserve [Roll Forward]
Beginning balance	3	4	6
Charged to expense	33	33	22
Cash payments	(31)	(31)	(23)
Non-cash settlements	(2)	(3)	(1)
Ending balance	$ 3	$ 3	$ 4