Changes in the Escrow Account (Detail) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
		Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Jun. 21, 2016 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Preferred Stock Available to Recover Covered Losses, Value, As-converted		$ 6,504
Preferred Stock Available to Recover Covered Losses, Value		5,717
Escrow Account [Roll Forward]
Litigation Escrow Account Balance, Beginning of Period		1,072	$ 1,498
Litigation Escrow Account Balance, End of Period		1,027	1,072	$ 1,498
VE Covered Loss, Maximum Amount of Loss to Allow Adjustment of Conversion Rate during Six-month Period		20
Right to recover for covered losses (Note 3)		(34)	0	$ 0	$ 25
Initial conversion rate of UK&I and Europe preferred stock into class A common or class A equivalent preferred stock					13.952
Preferred Stock Available to Recover Covered Losses, Value, As-converted, Net		6,470
Preferred Stock Available to Recover Covered Losses, Value, Net		$ 5,683
Closing Stock Price | $ / shares		$ 82.7
Opt-out Merchants
Escrow Account [Roll Forward]
Payments to Settlement Funds	[1]	$ (45)	$ (426)
MasterCard [Member]
Escrow Account [Roll Forward]
Omnibus Loss Sharing Agreement Percentage		33.3333%
Visa
Escrow Account [Roll Forward]
Omnibus Loss Sharing Agreement Percentage		66.6667%
Class A common stock
Escrow Account [Roll Forward]
Closing Stock Price | $ / shares		$ 82.70
Series B Preferred Stock
Restricted Cash and Cash Equivalents Items [Line Items]
Preferred Stock Available to Recover Covered Losses, Value, As-converted		$ 2,862
Preferred Stock Available to Recover Covered Losses, Value		$ 2,516
Escrow Account [Roll Forward]
Preferred stock, shares outstanding | shares		2	0
Series C Preferred Stock
Restricted Cash and Cash Equivalents Items [Line Items]
Preferred Stock Available to Recover Covered Losses, Value, As-converted		$ 3,642
Preferred Stock Available to Recover Covered Losses, Value		$ 3,201
Escrow Account [Roll Forward]
Preferred stock, shares outstanding | shares		3	0

[1] 1)These payments are associated with the interchange multidistrict litigation. See Note 20—Legal Matters.