Fair Value and Gross Unrealized Losses on Available-for-Sale Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 236		$ 714
Less than 12 months Unrealized Losses	(3)		(3)
12 months or more Fair Value	121		104
12 months or more Unrealized Losses	(3)		(2)
Total Fair Value	357		818
Total Unrealized Losses	(6)		(5)
Agency mortgage-backed securities | Residential mortgage backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value			73
Less than 12 months Unrealized Losses			(1)
Total Fair Value			73
Total Unrealized Losses			(1)	[1]
Agency mortgage-backed securities | Commercial mortgage backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value			355
Less than 12 months Unrealized Losses			(1)
Total Fair Value			355
Total Unrealized Losses			(1)
Asset-backed securities and other debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	236		286
Less than 12 months Unrealized Losses	(3)		(1)
12 months or more Fair Value	90		74
12 months or more Unrealized Losses	(2)		(1)
Total Fair Value	326		360
Total Unrealized Losses	(5)		(2)
Equity securities
Investments, Unrealized Loss Position [Line Items]
12 months or more Fair Value	31		30
12 months or more Unrealized Losses	(1)		(1)
Total Fair Value	31		30
Total Unrealized Losses	$ (1)	[2]	$ (1)	[2]

[1] Includes interest-only mortgage-backed securities of $158 and $175 as of March 31, 2015 and December 31, 2014, respectively, recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

[2] Equity securities consist of FHLB and FRB restricted stock holdings of $248 and $352, respectively, at March 31, 2015 and December 31, 2014, that are carried at cost, and certain mutual fund and equity security holdings.