Securities (Fair Value and Gross Unrealized Losses on Available-for-Sale Securities) (Detail) - USD ($) $ in Millions	Sep. 30, 2016		Dec. 31, 2015
Investments, Unrealized Loss Position
Less than 12 months Fair Value	$ 551		$ 8,248
Less than 12 months Unrealized Losses	(9)		(90)
12 months or more Fair Value	496		263
12 months or more Unrealized Losses	(12)		(11)
Total Fair Value	1,047		8,511
Total Unrealized Losses	(21)		(101)
Agency mortgage-backed securities | Residential mortgage backed securities
Investments, Unrealized Loss Position
Less than 12 months Fair Value	0		2,903
Less than 12 months Unrealized Losses	0		(13)
12 months or more Fair Value	193		0
12 months or more Unrealized Losses	(2)		0
Total Fair Value	193		2,903
Total Unrealized Losses	(2)	[1]	(13)	[2]
Agency mortgage-backed securities | Commercial mortgage backed securities
Investments, Unrealized Loss Position
Less than 12 months Fair Value	106		3,111
Less than 12 months Unrealized Losses	(1)		(33)
12 months or more Fair Value	0		0
12 months or more Unrealized Losses	0		0
Total Fair Value	106		3,111
Total Unrealized Losses	(1)		(33)
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Investments, Unrealized Loss Position
Less than 12 months Fair Value	0		1,610
Less than 12 months Unrealized Losses	0		(32)
12 months or more Fair Value	0		0
12 months or more Unrealized Losses	0		0
Total Fair Value	0		1,610
Total Unrealized Losses	0		(32)
Asset-backed securities and other debt securities
Investments, Unrealized Loss Position
Less than 12 months Fair Value	445		623
Less than 12 months Unrealized Losses	(8)		(11)
12 months or more Fair Value	272		226
12 months or more Unrealized Losses	(9)		(10)
Total Fair Value	717		849
Total Unrealized Losses	(17)		(21)
Equity securities
Investments, Unrealized Loss Position
Less than 12 months Fair Value	0		1
Less than 12 months Unrealized Losses	0		(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 $ 33 as of September 30, 2016 , recorded at fair value with fair value changes re corded in securities gains, net , in the Condensed Consolidated Statement s of Income.

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

[3] Equity securities consist of FHLB, FRB and DTCC restricted stock holdings of $ 248 , $ 357 and $ 1 , respectively , at September 30, 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