Derivatives and Hedging Activities - Fair Value of Credit Derivatives Purchased and Sold (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Credit Derivatives [Line Items]
Purchased	$ 2	$ (2)	$ (3)
Credit derivatives, net	2	(2)	(3)
Single Name Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Purchased	(2)	(3)	(1)
Credit derivatives, net	(2)	(3)	(1)
Traded Credit Default Swap Indices [Member]
Credit Derivatives [Line Items]
Purchased	4	1	(2)
Credit derivatives, net	$ 4	$ 1	$ (2)