Derivatives and Hedging Activities - Fair Value of Derivative Assets by Type (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 1,274	$ 1,431	$ 1,451
Less: Related collateral	503	486	511
Total derivative assets	771	945	940
Interest rate [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	1,195	1,257	1,298
Foreign Exchange [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	24	64	71
Energy and commodity [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	51	96	65
Credit [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	4	12	15
Equity [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral		$ 2	$ 2