Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) $ in Millions		9 Months Ended
	Jan. 14, 2015 merchant	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jul. 23, 2015
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period		$ 1,456	$ 5
Balance at end of period		1,097	1,060
Interchange Multidistrict Litigation [Member]
Loss Contingency Accrual [Roll Forward]
Reestablishment of obligation related to interchange multidistrict litigation		$ 0	$ 1,056
Interchange Opt Out Litigation [Member]
Loss Contingencies [Line Items]
Rejoined Opt Out Merchant | merchant	1,179
Number of opt-out cases filed (more than)			45
Interchange Opt Out Litigation [Member] | Subsequent Event
Loss Contingencies [Line Items]
Sales Volume Of Opt Out Merchants Percent Settled				27.00%
U.K. Merchant Litigation [Member]
Loss Contingencies [Line Items]
Claim limitation period		6 years
Unsettled [Member]
Loss Contingency Accrual [Roll Forward]
Additional provision for legal matters		$ 3	$ 0
Settled [Member]
Loss Contingency Accrual [Roll Forward]
Payments on litigation matters		(362)	(1)
Covered Litigation [Member]
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period		1,449	0
Payments on litigation matters		(355)	0
Balance at end of period		1,094	1,056
Covered Litigation [Member] | Interchange Multidistrict Litigation [Member]
Loss Contingency Accrual [Roll Forward]
Reestablishment of obligation related to interchange multidistrict litigation		$ 0	$ 1,056