Derivatives and Hedging Activities - Fair Value of Credit Derivatives Purchased and Sold (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Credit Derivatives [Line Items]
Purchased	$ (5)	$ (1)	$ (3)
Sold	1		3
Credit derivatives, net	(4)	(1)
Single Name Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Purchased	(4)	(1)	(4)
Sold	1	1	1
Credit derivatives, net	(3)		(3)
Traded Credit Default Swap Indices [Member]
Credit Derivatives [Line Items]
Purchased	(1)
Sold			3
Credit derivatives, net	(1)		3
Other [Member]
Credit Derivatives [Line Items]
Purchased			1
Sold		(1)	(1)
Credit derivatives, net		$ (1)