Guarantees and Contingent Liabilities - Summary of Other Guarantees and Contingent Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Guarantor Obligations [Line Items]
Carrying Amount	$ 436	$ 452
Standby letters of credit [Member]
Guarantor Obligations [Line Items]
Carrying Amount	80
Maximum Potential Future Payments	18,121
Third-party borrowing arrangements [Member]
Guarantor Obligations [Line Items]
Maximum Potential Future Payments	308
Securities lending indemnifications [Member]
Guarantor Obligations [Line Items]
Collateral Held	5,087
Maximum Potential Future Payments	4,944
Asset sales [Member]
Guarantor Obligations [Line Items]
Carrying Amount	313
Maximum Potential Future Payments	2,822
Merchant processing [Member]
Guarantor Obligations [Line Items]
Collateral Held	796
Carrying Amount	81
Maximum Potential Future Payments	79,390
Contingent consideration arrangements [Member]
Guarantor Obligations [Line Items]
Carrying Amount	12
Maximum Potential Future Payments	14
Tender option bond program guarantee [Member]
Guarantor Obligations [Line Items]
Collateral Held	5,176
Maximum Potential Future Payments	4,897
Minimum revenue guarantees [Member]
Guarantor Obligations [Line Items]
Carrying Amount	14
Maximum Potential Future Payments	15
Other [Member]
Guarantor Obligations [Line Items]
Carrying Amount	16
Maximum Potential Future Payments	$ 3,222