Guarantees and Contingent Liabilities - Summary of Other Guarantees and Contingent Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Standby letters of credit [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	69
Maximum Potential Future Payments	16,638
Third-party borrowing arrangements [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount
Maximum Potential Future Payments	16
Securities lending indemnifications [Member]
Guarantor Obligations [Line Items]
Collateral Held	5,008
Carrying Amount
Maximum Potential Future Payments	4,902
Asset sales [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	183
Maximum Potential Future Payments	3,786
Merchant processing [Member]
Guarantor Obligations [Line Items]
Collateral Held	839
Carrying Amount	71
Maximum Potential Future Payments	85,817
Contingent consideration arrangements [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	11
Maximum Potential Future Payments	12
Tender option bond program guarantee [Member]
Guarantor Obligations [Line Items]
Collateral Held	4,455
Carrying Amount
Maximum Potential Future Payments	4,349
Minimum revenue guarantees [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount	10
Maximum Potential Future Payments	10
Other [Member]
Guarantor Obligations [Line Items]
Collateral Held
Carrying Amount
Maximum Potential Future Payments	$ 374