Realized Gains and Losses Recognized in Income from Available-for-Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Gain (loss) on investments
Realized gains	$ 14		$ 29		$ 54		$ 57
Realized losses	(4)				(90)		(2)
OTTI	45		23		57		39
Net realized gains (losses)	$ (35)	[1]	$ 6	[1]	$ (93)	[1]	$ 16	[1]

[1] Excludes net gains on interest-only mortgage-backed securities of $40 for the three months ended September 30, 2013 and net gains on interest-only mortgage backed securities of $121 for the nine months ended September 30, 2013, respectively.