Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2015	Sep. 30, 2014
Investment securities:
Trading	$ 71	$ 69
Fair Value, Measurements, Recurring
Accrued liabilities
Visa Europe put option	255	145
Level 1 \| Fair Value, Measurements, Recurring
Prepaid and other current assets:
Fair value, total assets	5,078	4,580
Accrued liabilities
Fair value, total liabilities	0	0
Level 2 \| Fair Value, Measurements, Recurring
Prepaid and other current assets:
Fair value, total assets	3,146	2,761
Accrued liabilities
Fair value, total liabilities	8	6
Level 3 \| Fair Value, Measurements, Recurring
Prepaid and other current assets:
Fair value, total assets	7	7
Accrued liabilities
Fair value, total liabilities	255	145
Visa Europe put option \| Level 3 \| Fair Value, Measurements, Recurring
Accrued liabilities
Visa Europe put option	255	145
Foreign exchange derivative instruments \| Level 2 \| Fair Value, Measurements, Recurring
Accrued liabilities
Foreign exchange derivative instruments	8	6
Money market funds \| Level 1 \| Fair Value, Measurements, Recurring
Cash equivalents and restricted cash:
Cash equivalents and restricted cash:	2,239	2,277
Commercial paper \| Level 2 \| Fair Value, Measurements, Recurring
Cash equivalents and restricted cash:
Cash equivalents and restricted cash:	45	37
Equity securities \| Level 1 \| Fair Value, Measurements, Recurring
Investment securities:
Trading	71	69
Available-for-sale securities	12	58
U.S. government-sponsored debt securities \| Level 2 \| Fair Value, Measurements, Recurring
Investment securities:
Available-for-sale securities	2,482	2,162
U.S. Treasury securities \| Level 1 \| Fair Value, Measurements, Recurring
Investment securities:
Available-for-sale securities	2,756	2,176
Corporate debt securities \| Level 2 \| Fair Value, Measurements, Recurring
Investment securities:
Available-for-sale securities	548	522
Auction rate securities \| Level 3 \| Fair Value, Measurements, Recurring
Investment securities:
Available-for-sale securities	7	7
Foreign exchange derivative instruments \| Level 2 \| Fair Value, Measurements, Recurring
Prepaid and other current assets:
Prepaid and other current assets:	$ 71	$ 40

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Other Assets, Current [Abstract]

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