Commitments, Contingent Liabilities and Guarantees - Guarantees (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Financial guarantees:
Maximum Potential Undiscounted Future Payments	$ 13,775
Liability Recorded	129
Standby letters of credit [Member]
Financial guarantees:
Maximum Potential Undiscounted Future Payments	10,530
Liability Recorded	53
Recourse agreement with FNMA [Member]
Financial guarantees:
Maximum Potential Undiscounted Future Payments	1,158
Liability Recorded	7
Return guarantee agreement with LIHTC investors [Member]
Financial guarantees:
Maximum Potential Undiscounted Future Payments	20
Liability Recorded	20
Written put options [Member]
Financial guarantees:
Maximum Potential Undiscounted Future Payments	2,017
Liability Recorded	48
Default guarantees [Member]
Financial guarantees:
Maximum Potential Undiscounted Future Payments	50
Liability Recorded	$ 1