Guarantee Arrangements and Pledged Assets - Carrying Value and Contractual Amounts of our Sell Protection Credit Derivatives and Major Off-Balance Sheet Guarantee Arrangements (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Credit derivatives [Member]
Guarantor Obligations [Line Items]
Guarantee Arrangement for the benefit of Affiliates	$ 42,400	$ 44,200
Financial standby letters of credit, net of participations [Member]
Guarantor Obligations [Line Items]
Guarantee Arrangement for the benefit of Affiliates	$ 840	$ 808