Realized Gains and Losses Recognized in Income from Available-for-Sale Securities (Detail) - Available-for-sale Securities - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Realized gains		$ 15	$ 15
Realized losses		(4)	(2)
OTTI		(3)	(1)
Net realized gains (losses)	[1]	$ 8	$ 12

[1] Excludes net losses on interest-only mortgage-backed securities of $6 and $9 for the three months ended March 31, 2016 and March 31, 2015, respectively.