Realized Gains and Losses Recognized in Income from Available-for-Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Gain (loss) on investments
Realized gains	$ 27		$ 18
Realized losses	(5)		(25)
OTTI	(17)
Net realized gains (losses)	$ 5	[1]	$ (7)	[1]

[1] Excludes net gains on interest-only mortgage-backed securities of $1 and $24 for the three months ended March 31, 2014 and 2013, respectively.