Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) $ in Millions		1 Months Ended	6 Months Ended
	Feb. 17, 2017 case_filed	Mar. 31, 2017 USD ($) merchant	Mar. 31, 2017 USD ($) merchant	Mar. 31, 2016 USD ($)	Apr. 20, 2017	Nov. 30, 2016 plaintiff_class
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period			$ 981	$ 1,024
Balance at end of period		$ 996	$ 996	1,013
Case filed in Texas state court | case_filed	1
U.K. Merchant Litigation
Loss Contingency Accrual [Roll Forward]
Number of plaintiffs | merchant			150
Number of claims settled | merchant			15
Number of claims pending trial decision | merchant		1
Number of claims settled before trial | merchant			3
Number of claims settled during trial | merchant			12
Merchants with outstanding claims | merchant		130	130
Threatened Litigation | U.K. Merchant Litigation
Loss Contingency Accrual [Roll Forward]
Number of plaintiffs | merchant			30
Unsettled
Loss Contingency Accrual [Roll Forward]
Provision for uncovered legal matters			$ 17	1
Settled Litigation
Loss Contingency Accrual [Roll Forward]
Payments on litigation matters			(144)	(12)
U.S. Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period			978	1,023
Balance at end of period		$ 978	978	1,012
U.S. Covered Litigation | Settled Litigation
Loss Contingency Accrual [Roll Forward]
Payments on litigation matters			0	(11)
VE Territory Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period			2
Provision for uncovered legal matters			142	$ 0
Balance at end of period		$ 0	0
VE Territory Covered Litigation | Settled Litigation
Loss Contingency Accrual [Roll Forward]
Payments on litigation matters			$ (144)
Interchange Multidistrict Litigation
Loss Contingency Accrual [Roll Forward]
Number of putative classes of plaintiffs | plaintiff_class						2
Subsequent Event | Interchange Multidistrict Litigation
Loss Contingency Accrual [Roll Forward]
Merchants with settlement agreements (percent)					34.00%