Legal Matters Legal Matters - Accrued Litigation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012
Loss Contingency Accrual [Roll Forward]
Accrued Litigation, Beginning of Period	$ 4,386		$ 425
Interst accretion on settled matters	0		1
Accrued Litigation, End of Period	5		4,386
Unsettled
Loss Contingency Accrual [Roll Forward]
Provision for unsettled legal matters	3		4,100
Payments on unsettled and settled matters	(4,033)	[1]	0	[1]
Settled
Loss Contingency Accrual [Roll Forward]
Payments on unsettled and settled matters	$ (351)		$ (140)

[1] On December 10, 2012, 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. The settlement with the class plaintiffs is subject to final court approval, which the Company cannot assure will be received, and to the adjudication of any appeals. See further discussion below.