Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) (USD $) In Millions, unless otherwise specified							6 Months Ended
	Mar. 31, 2014		Dec. 31, 2012		Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2014 Unsettled		Mar. 31, 2013 Unsettled		Mar. 31, 2014 Settled	Mar. 31, 2013 Settled
Loss Contingency Accrual [Roll Forward]
Balance at October 1	$ 1,060		$ 6		$ 5	$ 4,386
Provision for unsettled matters									4
Reestablishment of obligation related to interchange multidistrict litigation	1,056	[1]		[1]
Payments on litigation matters								[1]	(4,033)	[1]	(1)	(351)
Balance at March 31	$ 1,060		$ 6		$ 5	$ 4,386

[1] In fiscal 2013, the Company paid approximately $4.0 billion from the litigation escrow account into a settlement fund established pursuant to the definitive class settlement agreement in the interchange multidistrict litigation. Under the settlement agreement, if class members opt-out (“opt-out merchants”) of the damages portion of the class settlement, the defendants are entitled to receive payments of no more than 25% of the original cash payments made into the settlement fund, based on the percentage of payment card sales volume for a defined period attributable to merchants who opted out (the "takedown payments"). On January 14, 2014, the court entered the final judgment order approving the settlement with the class plaintiffs in the interchange multidistrict litigation proceedings, which is subject to the adjudication of any appeals. Takedown payments of approximately $1.1 billion were received on January 27, 2014, and deposited into the Company’s litigation escrow account. The deposit into the litigation escrow account and a related increase in accrued litigation to address opt-out claims were recorded in the second quarter of fiscal 2014. See further discussion below.