Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions					12 Months Ended
	Sep. 30, 2019 USD ($) shares	Sep. 30, 2018 shares	Sep. 30, 2016	Jun. 21, 2016	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($) shares	Oct. 22, 2019 $ / shares	Jan. 31, 2019 USD ($)
Class of Stock [Line Items]
Reduction in as-converted stock (in shares) | shares					58,000,000
Reduction in as-converted stock (in dollars per share) | $ / shares					$ 154.62
Operating cash on hand used to repurchase of class A common stock					$ 8,607	$ 7,192	$ 6,891
Deposits into the litigation escrow account					300	600
Recovery through conversion rate adjustment					8
Stock repurchase program, authorized amount									$ 8,500
Stock repurchase plan, remaining authorized funds	$ 4,100				4,100
Dividends, paid					$ 2,300
Dividends paid, quarterly, per share (in dollars per share) | $ / shares					$ 0.25
Subsequent Event
Class of Stock [Line Items]
Dividends declared, quarterly, per share amount (in dollars per share) | $ / shares								$ 0.30
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, conversion rate	12.936	12.9550	13.952
Recovery through conversion rate adjustment					$ 6	$ 35	$ 190
Preferred stock, shares outstanding (in shares) | shares	2,000,000	2,000,000			2,000,000	2,000,000
Class A common stock
Class of Stock [Line Items]
Shares repurchased in the open market (in shares) | shares					56,000,000	58,000,000	77,000,000
Operating cash on hand used to repurchase of class A common stock					$ 8,607	$ 7,192	$ 6,891
Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares) | shares	5,000,000	5,000,000			5,000,000	5,000,000
Preferred Stock
Class of Stock [Line Items]
Recovery through conversion rate adjustment					$ (8)	$ (56)	$ (191)
Preferred stock, shares outstanding (in shares) | shares	5,000,000	5,000,000			5,000,000	5,000,000
Preferred Stock | Series B Preferred Stock
Class of Stock [Line Items]
Recovery through conversion rate adjustment					$ 6
Share Repurchase Program Aggregate | Class C common stock
Class of Stock [Line Items]
Shares of class C common stock released from transfer restrictions, converted to class A common stock (in shares) | shares					140,000,000
Visa Europe
Class of Stock [Line Items]
Number of convertible debt instruments issued				3
Visa Europe | Class A equivalent preferred stock
Class of Stock [Line Items]
Preferred stock, conversion rate					100