Summary of Significant Accounting Policies (Details) $ in Millions	3 Months Ended			9 Months Ended
	Jun. 30, 2017 USD ($) country	Jun. 30, 2016 USD ($)	[1]	Jun. 30, 2017 USD ($) country	Jun. 30, 2016 USD ($)
New Accounting Pronouncement, Early Adoption [Line Items]
Number of countries in which entity operates (more than) | country	200			200
Income tax provision (Note 12)	$ 855	$ 10		$ 4,036	$ 1,442	[1]
Increase to net cash provided by operating activities				6,441	3,122
Increase in net cash used in financing activities				(6,304)	$ 9,468
New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncement, Early Adoption [Line Items]
Income tax provision (Note 12)	$ (13)			(59)
Increase to net cash provided by operating activities				(59)
Increase in net cash used in financing activities				$ (59)

[1] The Company did not include Visa Europe's financial results in the Company's unaudited consolidated statements of operations from the acquisition date, June 21, 2016, through June 30, 2016 as the impact was immaterial. The dilutive impact of the outstanding shares of series B and C convertible participating preferred stock from June 21, 2016 through June 30, 2016 was also not included in the calculation of basic or diluted earnings per share as the effect was immaterial. See Note 2—Visa Europe and Note 10—Earnings Per Share to these unaudited consolidated financial statements.