Summary of Other Guarantees and Contingent Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Guarantor Obligations [Line Items]
Carrying Amount	$ 423		$ 359
Standby letters of credit
Guarantor Obligations [Line Items]
Carrying Amount	81
Maximum Potential Future Payments	18,323
Third-party borrowing arrangements
Guarantor Obligations [Line Items]
Maximum Potential Future Payments	299
Securities lending indemnifications
Guarantor Obligations [Line Items]
Collateral Held	8,982
Maximum Potential Future Payments	8,737
Asset sales
Guarantor Obligations [Line Items]
Carrying Amount	305	[1]
Maximum Potential Future Payments	2,710	[1]
Merchant processing
Guarantor Obligations [Line Items]
Collateral Held	772
Carrying Amount	80
Maximum Potential Future Payments	81,280
Contingent consideration arrangements
Guarantor Obligations [Line Items]
Carrying Amount	3
Maximum Potential Future Payments	6
Tender option bond program guarantee
Guarantor Obligations [Line Items]
Collateral Held	5,329
Maximum Potential Future Payments	5,047
Minimum revenue guarantees
Guarantor Obligations [Line Items]
Carrying Amount	17
Maximum Potential Future Payments	31
Other
Guarantor Obligations [Line Items]
Carrying Amount	18
Maximum Potential Future Payments	$ 3,436

[1] The maximum potential future payments do not include loan sales where the Company provides standard representation and warranties to the buyer against losses related to loan underwriting documentation defects that may have existed at the time of sale that generally are identified after the occurrence of a triggering event such as delinquency. For these types of loan sales, the maximum potential future payments is generally the unpaid principal balance of loans sold measured at the end of the current reporting period. Actual losses will be significantly less than the maximum exposure, as only a fraction of loans sold will have a representation and warranty breach, and any losses on repurchase would generally be mitigated by any collateral held against the loans.