Available-for-Sale and Held-to-Maturity Securities (Detail) - USD ($) $ in Millions		Mar. 31, 2016		Dec. 31, 2015
Investment Holdings [Line Items]
Available-for-sale securities, fair value	[1]	$ 29,891		$ 29,044
Available-for-sale securities, unrealized losses		(22)		(101)
Available-for-sale securities, unrealized gains		1,075		467
Available-for-sale and other securities, Amortized Cost		28,838		28,678
Held-to-maturity securities, fair value		64		70
Held-to-maturity securities, amortized cost	[2]	64		70
U.S. Treasury and federal agencies
Investment Holdings [Line Items]
Available-for-sale securities, fair value		1,161		1,187
Available-for-sale securities, unrealized gains		30		32
Available-for-sale and other securities, Amortized Cost		1,131		1,155
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, fair value		52		52
Available-for-sale securities, unrealized gains		2		2
Available-for-sale and other securities, Amortized Cost		50		50
Held-to-maturity securities, fair value		62		68
Held-to-maturity securities, amortized cost		62		68
Agency mortgage-backed securities | Residential mortgage backed securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		15,129	[3]	15,081	[4]
Available-for-sale securities, unrealized losses		(2)	[3]	(13)	[4]
Available-for-sale securities, unrealized gains		545	[3]	283	[4]
Available-for-sale and other securities, Amortized Cost		14,586	[3]	14,811	[4]
Agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		8,205		7,862
Available-for-sale securities, unrealized losses				(33)
Available-for-sale securities, unrealized gains		368		100
Available-for-sale and other securities, Amortized Cost		7,837		7,795
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		3,120		2,804
Available-for-sale securities, unrealized losses				(32)
Available-for-sale securities, unrealized gains		115		35
Available-for-sale and other securities, Amortized Cost		3,005		2,801
Asset-backed securities and other debt securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		1,520		1,355
Available-for-sale securities, unrealized losses		(19)		(21)
Available-for-sale securities, unrealized gains		13		13
Available-for-sale and other securities, Amortized Cost		1,526		1,363
Held-to-maturity securities, fair value		2		2
Held-to-maturity securities, amortized cost		2		2
Equity securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		704	[5]	703	[6]
Available-for-sale securities, unrealized losses		(1)	[5]	(2)	[6]
Available-for-sale securities, unrealized gains		2	[5]	2	[6]
Available-for-sale and other securities, Amortized Cost		$ 703	[5]	$ 703	[6]

[1] Amortized cost of $28,838 and $28,678 at March 31, 2016 and December 31, 2015, respectively.

[2] Fair value of $64 and $70 at March 31, 2016 and December 31, 2015, respectively.

[3] 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.

[4] 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.

[5] 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.

[6] 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