Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Millions		Jun. 30, 2018		Dec. 31, 2017
Assets:
Available-for-sale debt securities, fair value	[1]	$ 31,961		$ 31,751
Trading debt securities		280		492
Equity securities		475		439
Commercial
Assets:
Loans held for sale measured at FV		8		0
Residential mortgage loans
Assets:
Loans measured at FV		162		137
Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		31,347	[2]	31,139	[3]
Trading debt securities		280		492
Equity securities		475		439
Residential mortgage loans held for sale		658		399
Loans measured at FV	[4]	162		137
Loans held for sale measured at FV		8
Mortgage servicing rights		959	[2],[5]	858
Derivative assets	[6]	945		823
Total assets		34,834		34,287
Liabilities:
Derivative liabilities	[7]	859		602
Short positions	[7]	139		31
Total liabilities		998		633
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		540		514
Liabilities:
Derivative liabilities		316		178
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		121		124
Liabilities:
Derivative liabilities		109		120
Equity Contract | Fair value, recurring
Assets:
Equity securities				20
Liabilities:
Derivative liabilities		164		137
Commodity Contract | Fair value, recurring
Assets:
Derivative assets		284		165
Liabilities:
Derivative liabilities		270		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		19		12
Obligations of states and political subdivisions
Assets:
Available-for-sale debt securities, fair value		35		44
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		35		44
Trading debt securities		58		22
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale debt securities, fair value		16,094		15,319	[8]
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		16,094		15,319
Trading debt securities		75		395
Agency mortgage-backed securities | Commercial mortgage backed securities
Assets:
Available-for-sale debt securities, fair value		10,038		10,167
Agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		10,038		10,167
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Assets:
Available-for-sale debt securities, fair value		3,086		3,293
Non-agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		3,086		3,293
Asset-backed securities and other debt securities
Assets:
Available-for-sale debt securities, fair value		1,998		2,218
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		1,998		2,218
Trading debt securities		128		63
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		96	[2],[9]	98	[3],[10]
Trading debt securities		10	[9]	1	[10]
Equity securities		474		438
Derivative assets	[6]	34	[9]	40	[10]
Total assets		614	[9]	577	[10]
Liabilities:
Derivative liabilities	[7]	99	[9]	39	[10]
Short positions	[7]	88	[9]	25	[10]
Total liabilities		187	[9]	64	[10]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		0	[9]	1	[10]
Liabilities:
Derivative liabilities		4	[9]	1	[10]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		34	[9]	39	[10]
Liabilities:
Derivative liabilities		95	[9]	38	[10]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		96	[9]	98	[10]
Trading debt securities		10	[9]	1
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		31,251	[2],[9]	31,041	[3],[10]
Trading debt securities		270	[9]	491	[10]
Equity securities		1		1
Residential mortgage loans held for sale		658	[9]	399	[10]
Loans held for sale measured at FV	[9]	8
Derivative assets	[6]	900	[9]	775	[10]
Total assets		33,088	[9]	32,707	[10]
Liabilities:
Derivative liabilities	[7]	589	[9]	421	[10]
Short positions	[7]	51	[9]	6	[10]
Total liabilities		640	[9]	427	[10]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		529	[9]	505	[10]
Liabilities:
Derivative liabilities		305	[9]	172	[10]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		121	[9]	124	[10]
Liabilities:
Derivative liabilities		109	[9]	120	[10]
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		250	[9]	126	[10]
Liabilities:
Derivative liabilities		175	[9]	129	[10]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	[9]	0	[10]
Trading debt securities		9	[9]	11	[10]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		35	[9]	44	[10]
Trading debt securities		58	[9]	22	[10]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		16,094	[9]	15,319	[10]
Trading debt securities		75	[9]	395	[10]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		10,038	[9]	10,167	[10]
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		3,086	[9]	3,293	[10]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		1,998	[9]	2,218	[10]
Trading debt securities		128	[9]	63	[10]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Loans measured at FV	[4]	162		137
Mortgage servicing rights		959		858
Derivative assets	[6]	11		8
Total assets		1,132		1,003
Liabilities:
Derivative liabilities	[7]	171		142
Total liabilities		171		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		$ 164		$ 137

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

[2] Excludes FHLB, FRB and DTCC restricted stock holdings totaling $ 248 , $ 364 and $ 2 , respectively, at June 30, 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] For both the six months ended June 30, 2018 and 2017 , dividends were $ 6 37.50 per preferred shares for Perpetual Preferred Stock, Series H, $ 828.12 per preferred share for Perpetual Preferred Stock, Series I and $ 612.50 per preferred share for Perpetual Preferred Stock, Series J.

[6] Included in other assets in the Condensed Consolidated Balance Sheets.

[7] Included in other liabilities in the Condensed Consolidat ed Balance Sheets.

[8] 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.

[9] During both the three and six months ended June 30, 2018 , no assets or liabilities were transferred between Level 1 and Level 2.

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