Derivatives and Hedging Activities - Fair Value of Credit Derivatives Purchased and Sold (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Credit Derivatives [Line Items]
Purchased	$ 3	$ 10
Sold	(4)	(8)
Credit derivatives, net	(1)	2
Single name credit default swaps [Member]
Credit Derivatives [Line Items]
Purchased	3	3
Sold	(3)	(1)
Credit derivatives, net		2
Traded credit default swap indices [Member]
Credit Derivatives [Line Items]
Purchased		6
Sold		(6)
Credit derivatives, net
Other [Member]
Credit Derivatives [Line Items]
Purchased		1
Sold	(1)	(1)
Credit derivatives, net	$ (1)