Realized Gains and Losses Recognized in Income from Available-for-Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Gain (loss) on investments
Realized gains	$ 14		$ 22		$ 41		$ 40
Realized losses			(60)		(5)		(86)
OTTI			(12)		(17)		(12)
Net realized gains (losses)	$ 14	[1]	$ (50)	[1]	$ 19	[1]	$ (58)	[1]

[1] Excludes net losses on interest-only mortgage-backed securities of $8 and $7 for the three and six months ended June 30, 2014, respectively, and net gains on interest-only mortgage-backed securities of $56 and $81 for the three and six months ended June 30, 2013, respectively.