Securities (Investment Securities) (Detail) - USD ($) $ in Millions		Jun. 30, 2018		Dec. 31, 2017
Investment Holdings
Available-for-sale debt securities, fair value	[1]	$ 31,961		$ 31,751
Available-for-sale debt securities, unrealized losses		(702)		(134)
Available-for-sale debt securities, unrealized gains		74		308
Available-for-sale debt securities, amortized cost		32,589		31,577
Held-to-maturity securities, fair value		19		24
Held-to-maturity, unrealized losses		0		0
Held-to-maturity, unrealized gains		0		0
Held-to-maturity securities, amortized cost	[2]	19		24
Trading debt securities, fair value		280		492
Equity securities, fair value		475		439
U.S. Treasury and federal agencies
Investment Holdings
Available-for-sale debt securities, fair value		96		98
Available-for-sale debt securities, unrealized losses		(2)		0
Available-for-sale debt securities, unrealized gains		0		0
Available-for-sale debt securities, amortized cost		98		98
Obligations of states and political subdivisions
Investment Holdings
Available-for-sale debt securities, fair value		35		44
Available-for-sale debt securities, unrealized losses		0		0
Available-for-sale debt securities, unrealized gains		1		1
Available-for-sale debt securities, amortized cost		34		43
Held-to-maturity securities, fair value		17		22
Held-to-maturity, unrealized losses		0		0
Held-to-maturity, unrealized gains		0		0
Held-to-maturity securities, amortized cost		17		22
Agency mortgage-backed securities | Residential mortgage backed securities
Investment Holdings
Available-for-sale debt securities, fair value		16,094		15,319	[3]
Available-for-sale debt securities, unrealized losses		(346)		(80)	[3]
Available-for-sale debt securities, unrealized gains		35		118
Available-for-sale debt securities, amortized cost		16,405		15,281
Agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings
Available-for-sale debt securities, fair value		10,038		10,167
Available-for-sale debt securities, unrealized losses		(277)		(38)
Available-for-sale debt securities, unrealized gains		7		92
Available-for-sale debt securities, amortized cost		10,308		10,113
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings
Available-for-sale debt securities, fair value		3,086		3,293
Available-for-sale debt securities, unrealized losses		(68)		(5)
Available-for-sale debt securities, unrealized gains		5		51
Available-for-sale debt securities, amortized cost		3,149		3,247
Asset-backed securities and other debt securities
Investment Holdings
Available-for-sale debt securities, fair value		1,998		2,218
Available-for-sale debt securities, unrealized losses		(9)		(11)
Available-for-sale debt securities, unrealized gains		26		46
Available-for-sale debt securities, amortized cost		1,981		2,183
Held-to-maturity securities, fair value		2		2
Held-to-maturity, unrealized losses		0		0
Held-to-maturity, unrealized gains		0		0
Held-to-maturity securities, amortized cost		2		2
Other securities
Investment Holdings
Available-for-sale debt securities, fair value		614	[4]	612	[5]
Available-for-sale debt securities, unrealized losses		0	[4]	0	[5]
Available-for-sale debt securities, unrealized gains		0	[4]	0	[5]
Available-for-sale debt securities, amortized cost		$ 614	[4]	$ 612	[5]

[1] Amortized cost of $ 32,589 and $ 31,577 at June 30, 2018 and December 31, 2017 , respectively.

[2] Fair value of $ 19 and $ 24 at June 30, 2018 and December 31, 2017 , respectively.

[3] Includes interest-only mortgage-backed securities of $ 34 as of December 31, 2017 , recorded at fair value with fair value changes recorded in securities gains, net, in the Consolidated Statements of Income.

[4] Excludes FHLB, FRB and DTCC restricted stock holdings totaling $ 248 , $ 364 and $ 2 , respectively, at June 30, 2018 .

[5] Excludes FHLB, FRB , and DTCC restricted stock holdings totaling $ 248 , $ 362 and $ 2 , respectively, at December 31, 2017 .