Securities (Available-for-Sale and Held-to-Maturity Securities) (Detail) - USD ($) $ in Millions		Sep. 30, 2016		Dec. 31, 2015
Investment Holdings
Available-for-sale securities, fair value	[1]	$ 30,689		$ 29,044
Available-for-sale securities, unrealized losses		(21)		(101)
Available-for-sale securities, unrealized gains		1,224		467
Available-for-sale and other securities, Amortized Cost		29,486		28,678
Held-to-maturity securities, fair value		56		70
Held-to-maturity, unrealized losses		0		0
Held-to-maturity, unrealized gains		0		0
Held-to-maturity securities, amortized cost	[2]	56		70
U.S. Treasury and federal agencies
Investment Holdings
Available-for-sale securities, fair value		881		1,187
Available-for-sale securities, unrealized losses		0		0
Available-for-sale securities, unrealized gains		15		32
Available-for-sale and other securities, Amortized Cost		866		1,155
Obligations of states and political subdivisions
Investment Holdings
Available-for-sale securities, fair value		52		52
Available-for-sale securities, unrealized losses		0		0
Available-for-sale securities, unrealized gains		3		2
Available-for-sale and other securities, Amortized Cost		49		50
Held-to-maturity securities, fair value		55		68
Held-to-maturity, unrealized losses		0		0
Held-to-maturity, unrealized gains		0		0
Held-to-maturity securities, amortized cost		55		68
Agency mortgage-backed securities | Residential mortgage backed securities
Investment Holdings
Available-for-sale securities, fair value		15,188	[3]	15,081	[4]
Available-for-sale securities, unrealized losses		(2)	[3]	(13)	[4]
Available-for-sale securities, unrealized gains		519	[3]	283	[4]
Available-for-sale and other securities, Amortized Cost		14,671	[3]	14,811	[4]
Agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings
Available-for-sale securities, fair value		8,950		7,862
Available-for-sale securities, unrealized losses		(1)		(33)
Available-for-sale securities, unrealized gains		502		100
Available-for-sale and other securities, Amortized Cost		8,449		7,795
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings
Available-for-sale securities, fair value		2,834		2,804
Available-for-sale securities, unrealized losses		0		(32)
Available-for-sale securities, unrealized gains		151		35
Available-for-sale and other securities, Amortized Cost		2,683		2,801
Asset-backed securities and other debt securities
Investment Holdings
Available-for-sale securities, fair value		2,083		1,355
Available-for-sale securities, unrealized losses		(17)		(21)
Available-for-sale securities, unrealized gains		31		13
Available-for-sale and other securities, Amortized Cost		2,069		1,363
Held-to-maturity securities, fair value		1		2
Held-to-maturity, unrealized losses		0		0
Held-to-maturity, unrealized gains		0		0
Held-to-maturity securities, amortized cost		1		2
Equity securities
Investment Holdings
Available-for-sale securities, fair value		701	[5]	703	[6]
Available-for-sale securities, unrealized losses		(1)	[5]	(2)	[6]
Available-for-sale securities, unrealized gains		3	[5]	2	[6]
Available-for-sale and other securities, Amortized Cost		$ 699	[5]	$ 703	[6]

[1] Amortized cost of $ 29,486 and $ 28,678 at September 30, 2016 and Dec ember 31, 2015 , respectively.

[2] Fair value of $ 56 and $ 70 at September 30, 2016 and December 31, 2015 , respectively.

[3] 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.

[4] 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.

[5] 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.

[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