Guarantee Arrangements and Pledged Assets - Carrying Value and Contractual Amounts of our Sell Protection Credit Derivatives and Major Off-Balance Sheet Guarantee Arrangements (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Guarantor Obligations [Line Items]
Carrying Value	$ (1,194)	$ (7,759)
Notional/Maximum Exposure to Loss	272,655	338,865
Credit derivatives [Member]
Guarantor Obligations [Line Items]
Carrying Value	(1,194)	(7,759)
Notional/Maximum Exposure to Loss	262,985	330,395
Financial standby letters of credit, net of participations [Member]
Guarantor Obligations [Line Items]
Notional/Maximum Exposure to Loss	5,097	4,705
Performance (non-financial) guarantees [Member]
Guarantor Obligations [Line Items]
Notional/Maximum Exposure to Loss	3,023	3,088
Liquidity asset purchase agreements [Member]
Guarantor Obligations [Line Items]
Notional/Maximum Exposure to Loss	$ 1,550	$ 677