Legal Matters - Additional Information (Detail) $ in Millions						1 Months Ended		3 Months Ended	12 Months Ended			24 Months Ended	31 Months Ended	36 Months Ended	60 Months Ended
	Jan. 27, 2014 USD ($)	Dec. 16, 2013 USD ($)	Dec. 10, 2012 USD ($)	Oct. 29, 2012 USD ($)	Oct. 19, 2012	Oct. 31, 2011 financial_institution	Dec. 31, 2010 financial_institution entity	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) litigation_case case_filed	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 merchant	Sep. 30, 2015 merchant	Sep. 30, 2016 USD ($) case_filed	Dec. 31, 2004 state	Oct. 11, 2012 atm_operator
Loss Contingencies [Line Items]
Distribution to class merchants, rate amount					0.10%
Distribution to class merchants, period
Consecutive months of distribution to class merchants					8 months
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]
Payments for legal settlements	$ 4,000		$ 4,000								$ 4,000
Individual Plaintiffs
Loss Contingencies [Line Items]
Payments for legal settlements				$ 350
Consumer Interchange Litigation
Loss Contingencies [Line Items]
Damages sought by plaintiff from all defendants		$ 54,000
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%
Indirect Purchaser Actions
Loss Contingencies [Line Items]
Number of states where consumers reside | state															19
U.K. Merchant Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant												100
Canadian Competition Proceedings
Loss Contingencies [Line Items]
Number of Financial Institutions | financial_institution							10
Number of MasterCard entities | entity							2
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
Settled Litigation
Loss Contingencies [Line Items]
Payments on unsettled and settled matters									$ (47)	$ (446)
Threatened Litigation | Europe Interchange Rate Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | merchant													30
Covered Litigation | Interchange Multidistrict Litigation
Loss Contingencies [Line Items]
Provision for legal matters	$ 1,100
Unsettled
Loss Contingencies [Line Items]
Provision for legal matters									$ 2	$ 14
Covered Litigation
Loss Contingencies [Line Items]
Deposits into litigation escrow account								$ 450
Covered Litigation | Settled Litigation
Loss Contingencies [Line Items]
Payments on unsettled and settled matters														$ (528)
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