Legal and Regulatory Proceedings - Additional Information (Detail) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2009	Sep. 30, 2012	Dec. 31, 2008 Visa Litigation [Member]	Sep. 30, 2012 Visa Litigation [Member]	Dec. 31, 2011 Visa Litigation [Member]	Sep. 30, 2011 Visa Litigation [Member]	Dec. 31, 2007 Visa Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Visa Indemnification Charges			$ 169,000,000
Reserves for litigation				50,000,000	49,000,000	31,000,000	3,000,000
Number of putative securities class action complaints	5
Number of cases that have been consolidated	5
Number of additional lawsuit filed	2
Number of alleging violations of ERISA that were dismissed	2
Amount in excess of amounts reserved		$ 52,000,000