Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Assets:
Available-for-sale debt securities, fair value	[1]	$ 31,819		$ 31,751
Trading debt securities		571		492
Equity securities		418		439
Commercial loans held for sale measured at FV		650		399
Commercial
Assets:
Commercial loans held for sale measured at FV		16		0
Residential mortgage loans
Assets:
Loans measured at FV		136		137
Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		31,207	[2]	31,139	[3]
Trading debt securities		571		492
Equity securities		418		439
Residential mortgage loans held for sale		650		399
Loans measured at FV	[4]	136	[5]	137
Commercial loans held for sale measured at FV		16
Mortgage servicing rights		926	[2],[6]	858
Derivative assets	[7]	865		823
Total assets		34,789		34,287
Liabilities:
Derivative liabilities	[8]	774		602
Short positions	[8]	126		31
Total liabilities		900		633
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		534		514
Liabilities:
Derivative liabilities		285		178
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		132		124
Liabilities:
Derivative liabilities		129		120
Equity Contract | Fair value, recurring
Assets:
Equity securities				20
Liabilities:
Derivative liabilities		165		137
Commodity Contract | Fair value, recurring
Assets:
Derivative assets		199		165
Liabilities:
Derivative liabilities		195		167
U.S. Treasury and federal agencies
Assets:
Available-for-sale debt securities, fair value		96		98
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		96		98
Trading debt securities		21		12
Obligations of states and political subdivisions
Assets:
Available-for-sale debt securities, fair value		44		44
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		44		44
Trading debt securities		52		22
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale debt securities, fair value		15,208		15,319	[9]
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		15,208		15,319
Trading debt securities		364		395
Agency mortgage-backed securities | Commercial mortgage backed securities
Assets:
Available-for-sale debt securities, fair value		10,455		10,167
Agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		10,455		10,167
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Assets:
Available-for-sale debt securities, fair value		3,190		3,293
Non-agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		3,190		3,293
Asset-backed securities and other debt securities
Assets:
Available-for-sale debt securities, fair value		2,214		2,218
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		2,214		2,218
Trading debt securities		134		63
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		96	[2],[10]	98	[3],[11]
Trading debt securities		0	[10]	1	[11]
Equity securities		417		438
Derivative assets	[7]	36	[10]	40	[11]
Total assets		549	[10]	577	[11]
Liabilities:
Derivative liabilities	[8]	58	[10]	39	[11]
Short positions	[8]	93	[10]	25	[11]
Total liabilities		151	[10]	64	[11]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		2	[10]	1	[11]
Liabilities:
Derivative liabilities		2	[10]	1	[11]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		34	[10]	39	[11]
Liabilities:
Derivative liabilities		56	[10]	38	[11]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		96	[10]	98	[11]
Trading debt securities		0	[10]	1
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		31,111	[2],[10]	31,041	[3],[11]
Trading debt securities		571	[10]	491	[11]
Equity securities		1		1
Residential mortgage loans held for sale		650	[10]	399	[11]
Commercial loans held for sale measured at FV	[10]	16
Derivative assets	[7]	818	[10]	775	[11]
Total assets		33,167	[10]	32,707	[11]
Liabilities:
Derivative liabilities	[8]	544	[10]	421	[11]
Short positions	[8]	33	[10]	6	[11]
Total liabilities		577	[10]	427	[11]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		521	[10]	505	[11]
Liabilities:
Derivative liabilities		276	[10]	172	[11]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		132	[10]	124	[11]
Liabilities:
Derivative liabilities		129	[10]	120	[11]
Fair Value, Inputs, Level 2 | Equity Contract | Fair value, recurring
Assets:
Equity securities				20
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		165	[10]	126	[11]
Liabilities:
Derivative liabilities		139	[10]	129	[11]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	[10]	0	[11]
Trading debt securities		21	[10]	11	[11]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		44	[10]	44	[11]
Trading debt securities		52	[10]	22	[11]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		15,208	[10]	15,319	[11]
Trading debt securities		364	[10]	395	[11]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		10,455	[10]	10,167	[11]
Fair Value, Inputs, Level 2 | Non-agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		3,190	[10]	3,293	[11]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		2,214	[10]	2,218	[11]
Trading debt securities		134	[10]	63	[11]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Loans measured at FV	[4]	136	[5]	137
Mortgage servicing rights		926		858
Derivative assets	[7]	11		8
Total assets		1,073		1,003
Liabilities:
Derivative liabilities	[8]	172		142
Total liabilities		172		142
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		11		8
Liabilities:
Derivative liabilities		7		5
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Liabilities:
Derivative liabilities		$ 165		$ 137

[1] Amortized cost of $ 32,230 and $ 31,577 at March 31, 2018 and December 31, 2017 , respectively.

[2] Excludes FHLB, FRB and DTCC restricted stock holdings totaling $ 248 , $ 362 and $ 2 , respectively, at March 31, 2018 .

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

[4] Includes residential mortgage loans originated as held for sale and subsequently transferred to held for investment.

[5] Includes residential mortgage loans originated as held for sale and subsequently transferred to held for investment.

[6] For both the three months ended March 31, 2018 and 2017 , dividends were $ 414.06 per preferred share for Perpetual Preferred Stock, Series I and $ 612.5 0 per preferred share for Perpetual Preferred Stock, Series J.

[7] Included in other assets in the Condensed Consolidated Balance S heets.

[8] Included in other liabilities in the Condensed Consolidated Balance Sheets.

[9] 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 Condensed Consolidated Statements of Income.

[10] During the three months ended March 31, 2018 , no assets or liabilities were transferred between Level 1 and Level 2.

[11] During the year ended December 31, 2017 , no assets or liabilities were transferred between Level 1 and Level 2.