Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Tax Credit Carryforward [Line Items]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit	$ 1,100
Tax Cuts And Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)	1,100
US income before taxes	8,088	$ 8,440	$ 5,839
Income tax provision	2,505	4,995	$ 2,021	[1]
Deferred tax assets, net	$ 941	$ 1,307
U.S. federal statutory rate	24.53%	35.00%	35.00%
Income tax provision, percent	20.00%	43.00%	25.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount	$ 161
Income tax expense benefit charitable contributions		$ 71
Visa Europe Framework Agreement loss	0	0	$ 1,877	[1]
Revaluation of Visa Europe put option			255
Income taxes receivable included in prepaid and other current assets	82	148
Income taxes payable included in accrued taxes as part of accrued liabilities	257	243
Accrued income taxes included in other long-term liabilities	2,400	1,100
Decreased Singapore tax as a result of the tax incentive agreement	$ (295)	$ (252)	$ (235)
Benefit of the tax incentive agreement on diluted net income per share	$ 0.13	$ 0.11	$ 0.10
Total unrecognized tax benefits exclusive of interest and penalties	$ 1,658	$ 1,353	$ 1,160
Unrecognized tax benefits, if recognized, would reduce the effective tax rate in a future period	1,200	1,100
Interest expense included in interest expense and administrative and other	15	23	15
Accrued penalties related to uncertain tax positions	0	1	3
Accrued interest related to uncertain tax positions in other long term liabilities	99	84
Accrued penalties related to uncertain tax positions in other long term liabilities	34
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	17
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	21
Foreign Country
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	137
Other Assets
Tax Credit Carryforward [Line Items]
Deferred tax assets, net	14	81
Non-current income tax receivable	689	755
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	$ 2,700	2,900	$ 2,500
Visa Europe
Tax Credit Carryforward [Line Items]
Income tax provision		$ 1,500

[1] The Company did not include Visa Europe’s financial results in the Company’s consolidated statements of operations from the acquisition date, June 21, 2016, through June 30, 2016 as the impact was immaterial. The Company’s consolidated statement of operations for the year ended September 30, 2016 includes Visa Europe’s financial results for the three months ended September 30, 2016.