Net Periodic Pension and Other Postretirement Plan Cost (Detail) - Pension Benefits - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0	$ 0	$ 13
Interest cost	32	36	40
Expected return on assets	(70)	(70)	(69)
Amortization of prior service credit	0	0	(1)
Amortization of actuarial loss	0	15	7
Curtailment gain	0	0	(8)
Settlement loss	3	15	13
Total net periodic benefit cost	(35)	(4)	(5)
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	4	6	1	[1]
Interest cost	12	11	3	[1]
Expected return on assets	(20)	(16)	(4)	[1]
Amortization of prior service credit	0	0	0	[1]
Amortization of actuarial loss	0	2	0	[1]
Curtailment gain	0	0	0	[1]
Settlement loss	0	0	0	[1]
Total net periodic benefit cost	$ (4)	$ 3	$ 0	[1]

[1] For fiscal 2016, the amounts represent the Visa Europe plans’ net pension benefit cost recognized from the Closing through September 30, 2016.