Guarantees and Contingent Liabilities - Summary of Other Guarantees and Contingent Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	71
Maximum Potential Future Payments	17,339
Third-Party Borrowing Arrangements [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount
Maximum Potential Future Payments	17
Securities Lending Indemnifications [Member]
Guarantor Obligations [Line Items]
Collateral Held	5,494
Carrying Amount
Maximum Potential Future Payments	5,326
Asset Sales [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	267
Maximum Potential Future Payments	3,250
Merchant Processing [Member]
Guarantor Obligations [Line Items]
Collateral Held	840
Carrying Amount	69
Maximum Potential Future Payments	86,584
Contingent Consideration Arrangements [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	14
Maximum Potential Future Payments	17
Tender Option Bond Program Guarantee [Member]
Guarantor Obligations [Line Items]
Collateral Held	4,762
Carrying Amount
Maximum Potential Future Payments	4,711
Minimum Revenue Guarantees [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	12
Maximum Potential Future Payments	12
Other [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	6
Maximum Potential Future Payments	$ 553