Information that Causes the Income Tax Expense to Differ from the Amount of Income Tax Determined by Applying the Applicable U.S. Federal Statutory Rate of 35% to Pretax Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2015
Income Tax Disclosure [Abstract]
U.S. federal income tax at statutory rate	$ 4,093	$ 2,804		$ 3,148
State income taxes, net of federal benefit	200	135		194
Non-U.S. tax effect, net of federal benefit	(641)	(553)		(327)
Remeasurement of deferred tax liability	0	(88)		0
Reversal of prior years tax reserves related to the resolution of uncertain tax positions	0	0		(239)
Revaluation of Visa Europe put option	0	(89)		0
Other, net	(172)	(188)		(109)
Income tax provision	$ 4,995	$ 2,021	[1]	$ 2,667
U.S. federal income tax at statutory rate, percent	35.00%	35.00%		35.00%
State income taxes, net of federal benefit, percent	2.00%	2.00%		2.00%
Non-U.S. tax effect, net of federal benefit, percent	(5.00%)	(7.00%)		(4.00%)
Remeasurement of deferred tax liability, percent	0.00%	(1.00%)		0.00%
Reversal of prior years tax reserves related to the resolution of uncertain tax positions, percent	0.00%	0.00%		(2.00%)
Revaluation of Visa Europe put option, percent	0.00%	(1.00%)		0.00%
Other, net, percent	(2.00%)	(3.00%)		(1.00%)
Income tax expense, percent	43.00%	25.00%		30.00%
Income Tax Reconciliation Deductions Qualified Production Activities Prior Years	$ 1,515	$ 0		$ 0
Effective Income Tax Rate Reconciliation Deductions Qualified Production Activities Prior Years	13.00%	0.00%		0.00%

[1] See Note 2—Visa Europe.