Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Sep. 30, 2011
Fair Value, Measurement Inputs, Disclosure [Line Items]
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	17.4x
Spot price to earnings, ratio	1740.00%
Incremental price to earnings differential compared to estimate	1.8x
Incremental price to earnings differential compared to estimate, ratio	180.00%
Incremental probability of exercise by Visa Europe	5.00%
Increase in put option value due to increase in probability of exercise	$ 18
Incremental P/E 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
Fair value adjustment for the Visa Europe put option		122
Available-for-sale gross unrealized gains	2		0
Available-for-sale gross unrealized losses	1		0
Fair Value, Measurements, Recurring
Fair Value, Measurement Inputs, Disclosure [Line Items]
Put option, fair value	145		145
Non Marketable Equity Investments
Fair Value, Measurement Inputs, Disclosure [Line Items]
Non-marketable equity investments	$ 89		$ 100