Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2015
Tax Credit Carryforward [Line Items]
US income before taxes	$ 8,440	$ 5,839		$ 7,214
Income tax provision	4,995	2,021	[1]	$ 2,667
Deferred tax assets, net	$ 1,307	$ 2,712
U.S. federal statutory rate	35.00%	35.00%		35.00%
Income tax provision, percent	43.00%	25.00%		30.00%
Income tax expense benefit charitable contributions	$ 71
Visa Europe Framework Agreement loss	0	$ 1,877	[1]	$ 0
Revaluation of Visa Europe put option		255
Unrecognized tax benefits, period increase (decrease)				296
Reversal of prior years tax reserves related to the resolution of uncertain tax positions	0	0		239
Income taxes receivable included in prepaid and other current assets	148	232
Income taxes payable included in accrued taxes as part of accrued liabilities	243	153
Accrued income taxes included in other long-term liabilities	1,092	911
Cumulative undistributed earnings of the Company's international subsidiaries intended to be reinvested indefinitely outside the U.S	12,900
Decreased Singapore tax as a result of the tax incentive agreement	$ (252)	$ (235)		$ (192)
Benefit of the tax incentive agreement on diluted net income per share	$ 0.11	$ 0.10		$ 0.08
Total unrecognized tax benefits exclusive of interest and penalties	$ 1,353	$ 1,160		$ 1,051
Unrecognized tax benefits, if recognized, would reduce the effective tax rate in a future period	1,100	926
Interest expense included in interest expense and administrative and other	23	15		6
Accrued penalties related to uncertain tax positions	1	3		1
Accrued interest related to uncertain tax positions in other long term liabilities	84	61
Accrued penalties related to uncertain tax positions in other long term liabilities	34	17
New Accounting Pronouncement, Early Adoption, Effect
Tax Credit Carryforward [Line Items]
Income tax provision	70
Federal
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	42
Federal foreign tax credit carryforward	30
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	27
Foreign Country
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	140
Other Assets
Tax Credit Carryforward [Line Items]
Deferred tax assets, net	81	22
Non-current income tax receivable	755	731
Visa Europe | Foreign Country
Tax Credit Carryforward [Line Items]
Tax benefit due to remeasurement of deferred tax liabilities		(88)
Non United States Customers
Tax Credit Carryforward [Line Items]
US income before taxes	2,900	$ 2,500		$ 2,400
Visa Europe
Tax Credit Carryforward [Line Items]
Income tax provision	$ 1,500

[1] See Note 2—Visa Europe.