Fair Value Measurements and Investments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2012
Fair Value, Measurement Inputs, Disclosure [Line Items]
Payments from litigation escrow account-Retrospective Responsibility Plan	$ 4,383	$ 140
Probability of exercise by Visa Europe	40.00%
P/E differential at the time of exercise	1.9x
P/E differential at the time of exercise, ratio	190.00%
Spot price to earnings	20x
Spot price to earnings, ratio	2000.00%
Incremental price to earnings differential compared to estimate	2.4x
Incremental price to earnings differential compared to estimate, ratio	240.00%
Incremental probability of exercise by Visa Europe	5.00%
Increase in put option value due to increase in probability of exercise	18
Incremental Assumed Price to Earnings Differential at Time of Exercise	1.0x
Incremental P/E differential at time of exercise, ratio	100.00%
Increase in put option value due to increase in price to earnings differential	84
Other than Temporary Impairment Losses, Investments	15
Equity method investments, reclassified as available-for-sale securities, carrying value	12
Available-for-sale securities, previously classified as equity method Investments, fair value disclosure	60
Available-for-sale securities, previously classified as equity method investments, gross unrealized gains	48
Available-for-sale securities, gross unrealized gains	54		4
Available-for-sale securities, gross unrealized losses	1		1
Fair Value, Measurements, Recurring
Fair Value, Measurement Inputs, Disclosure [Line Items]
Visa Europe put option	145		145
Level 3 | Fair Value, Measurements, Recurring | Liability
Fair Value, Measurement Inputs, Disclosure [Line Items]
Contingent Payments Fair Value Disclosure	0		12
Non Marketable Equity Investments
Fair Value, Measurement Inputs, Disclosure [Line Items]
Non-marketable equity investments	$ 56		$ 86