Legal Matters - Additional Information (Detail) $ in Millions				1 Months Ended			3 Months Ended	8 Months Ended	12 Months Ended		48 Months Ended
	Jan. 27, 2014 USD ($)	Dec. 10, 2012 USD ($)	Oct. 29, 2012 USD ($)	Nov. 30, 2016 litigation_case	Oct. 31, 2011 financial_institution	Dec. 31, 2010 financial_institution entity	Sep. 30, 2014 USD ($)	Aug. 10, 2013	Sep. 30, 2017 USD ($) litigation_case case_filed merchant	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) case_filed merchant	Oct. 11, 2011 atm_operator	Dec. 01, 2010 litigation_case
Loss Contingencies [Line Items]
Decrease in deferred tax assets reflecting the current tax deduction related to payments made in connection with the covered litigation									$ 978
Class Plaintiffs
Loss Contingencies [Line Items]
Settlement, Further Distribution of Default Interchange, Rate								0.10
Payments for legal settlements	$ 4,000	$ 4,000
Loss Contingency, Number of Cases Appointed Counsel | litigation_case				2
Loss contingency, further distributions, default period								8 months
Individual Plaintiffs
Loss Contingencies [Line Items]
Payments for legal settlements			$ 350
Interchange Opt Out Litigation
Loss Contingencies [Line Items]
Number of opt-out cases filed | case_filed									50		50
Settlements reached by percentage of sales volume of merchants who opted out									51.00%		51.00%
U.K. Merchant Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant											300
Damages sought, value											$ 1,000
Canadian Competition Proceedings
Loss Contingencies [Line Items]
Number of Financial Institutions | financial_institution						10
Canadian Merchant Litigation
Loss Contingencies [Line Items]
Number of claims pending | litigation_case													3
Number of claims dismissed | entity						3
National ATM Council Class Action
Loss Contingencies [Line Items]
Number of non-bank ATM operators | atm_operator												13
Consumer Class Actions
Loss Contingencies [Line Items]
Number of Financial Institutions | financial_institution					3
Number of claims pending | financial_institution					2
Unsettled
Loss Contingencies [Line Items]
Provision for legal matters									$ 19	$ 2
Settled Litigation
Loss Contingencies [Line Items]
Payments on unsettled and settled matters									$ (204)	(47)
Settled Litigation | U.K. Merchant Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant											75
Settled Litigation | Canadian Competition Proceedings
Loss Contingencies [Line Items]
Number of Financial Institutions | entity						5
U.S. Covered Litigation | Interchange Multidistrict Litigation
Loss Contingencies [Line Items]
Provision for legal matters	$ 1,100
Pending Litigation | U.K. Merchant Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant											200
Pending Litigation | Canadian Competition Proceedings
Loss Contingencies [Line Items]
Number of Financial Institutions | entity						1
Threatened Litigation | Europe Interchange Rate Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant									30
Visa, MasterCard, and Certain U.S. Financial Institutions | Interchange Opt Out Litigation
Loss Contingencies [Line Items]
Number of claims filed | litigation_case									4
Visa | Interchange Opt Out Litigation
Loss Contingencies [Line Items]
Number of claims filed | litigation_case									3
Visa | Canadian Merchant Litigation
Loss Contingencies [Line Items]
Number of claims pending | litigation_case													1
MasterCard | Canadian Merchant Litigation
Loss Contingencies [Line Items]
Number of claims pending | litigation_case													2
U.S. Covered Litigation
Loss Contingencies [Line Items]
Deposits into litigation escrow account							$ 450
U.S. Covered Litigation | Settled Litigation
Loss Contingencies [Line Items]
Payments on unsettled and settled matters									$ 0	$ (45)	$ (528)