Fair Value and Gross Unrealized Losses on Available-for-Sale Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2016		Dec. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 767		$ 8,248
Less than 12 months Unrealized Losses	(10)		(90)
12 months or more Fair Value	297		263
12 months or more Unrealized Losses	(12)		(11)
Total Fair Value	1,064		8,511
Total Unrealized Losses	(22)		(101)
Agency mortgage-backed securities | Residential mortgage backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	268		2,903
Less than 12 months Unrealized Losses	(2)		(13)
Total Fair Value	268		2,903
Total Unrealized Losses	(2)	[1]	(13)	[2]
Agency mortgage-backed securities | Commercial mortgage backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value			3,111
Less than 12 months Unrealized Losses			(33)
Total Fair Value			3,111
Total Unrealized Losses			(33)
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value			1,610
Less than 12 months Unrealized Losses			(32)
Total Fair Value			1,610
Total Unrealized Losses			(32)
Asset-backed securities and other debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	499		623
Less than 12 months Unrealized Losses	(8)		(11)
12 months or more Fair Value	266		226
12 months or more Unrealized Losses	(11)		(10)
Total Fair Value	765		849
Total Unrealized Losses	(19)		(21)
Equity securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value			1
Less than 12 months Unrealized Losses			(1)
12 months or more Fair Value	31		37
12 months or more Unrealized Losses	(1)		(1)
Total Fair Value	31		38
Total Unrealized Losses	$ (1)	[3]	$ (2)	[4]

[1] Includes interest-only mortgage-backed securities of $41 as of March 31, 2016 recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

[2] Includes interest-only mortgage-backed securities of $50 as of December 31, 2015, recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

[3] Equity securities consist of FHLB, FRB and DTCC restricted stock holdings of $248, $355 and $1, respectively, at March 31, 2016, that are carried at cost, and certain mutual fund and equity security holdings.

[4] Equity securities consist of FHLB, FRB and DTCC restricted stock holdings of $248, $355, and $1, respectively, at December 31, 2015, that are carried at cost, and certain mutual fund and equity security holdings