Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) $ in Millions	9 Months Ended
	Jun. 30, 2016 USD ($) case_filed merchant	Jun. 30, 2015 USD ($)	Jul. 21, 2016
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 1,024	$ 1,456
Provision for legal matters	1	3
Balance at end of period	$ 978	1,097
Interchange Opt Out Litigation
Loss Contingencies [Line Items]
Number of opt-out cases filed (more than) | case_filed	60
Interchange Opt Out Litigation | Subsequent Event
Loss Contingencies [Line Items]
Settlements reached by percentage of sales volume of merchants who opted out (percent)			51.00%
U.K. Merchant Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant	75
Settled
Loss Contingency Accrual [Roll Forward]
Payments on litigation matters	$ (47)	(362)
Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	1,023	1,449
Payments on litigation matters	(45)	(355)
Balance at end of period	$ 978	$ 1,094