Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended					9 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Effective income tax rate reconciliation, percent	17.00%			29.00%		20.00%	47.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount	$ 81	$ 80
Income Tax Expense (Benefit)	483			$ 855		$ 1,812	$ 4,036
Income Tax Expense Benefit Charitable Contributions					$ 71
Tax cuts and jobs act of 2017, incomplete accounting, deferred tax liability, provisional income tax (expense) benefit			$ 1,100
Tax cuts and jobs act of 2017, incomplete accounting, transition tax accumulated foreign earnings, provisional income tax expense (benefit)			$ 1,100
Increase in unrecognized tax benefits	244					237
Effective income tax rate reconciliation Unrecognized Tax Benefits that would Favorably Impact Effective Tax Rate	$ 69					$ 73
Forecast
Business Acquisition [Line Items]
Federal statutory income tax rate, percent								21.00%	24.50%
Visa Europe
Business Acquisition [Line Items]
Income Tax Expense (Benefit)					$ 1,500