Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Business Acquisition [Line Items]
Income tax expense (benefit)	$ 2,272	$ 734	$ 3,181	$ 1,432
Income tax expense (benefit), charitable contributions	$ (71)
Effective income tax rate reconciliation, percent	84.00%	30.00%	56.00%	28.00%
Revaluation of the Visa Europe put option		$ 255
Increase in unrecognized tax benefits	$ 23		$ 56
Effective income tax rate reconciliation Unrecognized Tax Benefits that would Favorably Impact Effective Tax Rate	69		97
New Accounting Pronouncement, Early Adoption, Effect
Business Acquisition [Line Items]
Income tax expense (benefit)	(20)		$ (46)
Visa Europe
Business Acquisition [Line Items]
Income tax expense (benefit)	$ 1,500