Summary of Significant Accounting Policies - Additional Information (Detail)			12 Months Ended
	Feb. 01, 2017 USD ($)	Mar. 19, 2015	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)	Jun. 21, 2016
Significant Accounting Policies [Line Items]
Number of Countries in which Entity Operates (more than)			200
Number of reportable segments			1
Payments to Acquire Available-for-sale Securities			$ 3,238,000,000	$ 10,426,000,000		$ 2,850,000,000
Proceeds from maturities and sales			5,012,000,000	9,119,000,000		1,925,000,000
Indefinite-lived intangible impairment	$ 0
Goodwill, impairment loss	$ 0
Income tax provision (Note 18)			4,995,000,000	2,021,000,000	[1]	2,667,000,000
Income to net cash provided by operating activities			9,208,000,000	5,574,000,000		6,584,000,000
Increase in net cash used in financing activities			(5,924,000,000)	7,477,000,000		$ (3,603,000,000)
New Accounting Pronouncement, Early Adoption, Effect
Significant Accounting Policies [Line Items]
Income tax provision (Note 18)			70,000,000
Income to net cash provided by operating activities			70,000,000
Increase in net cash used in financing activities			$ 70,000,000
Domestic
Significant Accounting Policies [Line Items]
Expected average employee future service period for United States plans (in years)			9 years
Non-U.S. Plans
Significant Accounting Policies [Line Items]
Expected average employee future service period for United States plans (in years)			11 years
Minimum
Significant Accounting Policies [Line Items]
Acquired long-lived intangible assets useful life			3 years
Maximum
Significant Accounting Policies [Line Items]
Acquired long-lived intangible assets useful life			15 years
Furniture and Fixtures | Minimum
Significant Accounting Policies [Line Items]
Estimated useful life			2 years
Furniture and Fixtures | Maximum
Significant Accounting Policies [Line Items]
Estimated useful life			10 years
Building Improvements | Minimum
Significant Accounting Policies [Line Items]
Estimated useful life			3 years
Building Improvements | Maximum
Significant Accounting Policies [Line Items]
Estimated useful life			40 years
Building
Significant Accounting Policies [Line Items]
Estimated useful life			40 years
Restatement Adjustment
Significant Accounting Policies [Line Items]
Payments to Acquire Available-for-sale Securities				(17,600,000,000)
Proceeds from maturities and sales				17,600,000,000
Scenario, Previously Reported
Significant Accounting Policies [Line Items]
Payments to Acquire Available-for-sale Securities				28,000,000,000
Proceeds from maturities and sales				$ 26,700,000,000
Class A common stock
Significant Accounting Policies [Line Items]
Common stock split, conversion ratio		4
Visa Europe
Significant Accounting Policies [Line Items]
Share capital of Visa Europe acquired (percent)							100.00%

[1] See Note 2—Visa Europe.