Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016
Assets:
Available-for-sale securities, fair value	[1]	$ 31,820		$ 31,183
Trading securities		862		410
Residential mortgage loans measured at fair value		137		143
Derivative assets		823		1,057
Fair value, recurring
Assets:
Available-for-sale securities, fair value		31,208	[2]	30,576	[3]
Trading securities		862		410
Residential mortgage loans held for sale		399		686
Residential mortgage loans measured at fair value		137	[4]	143	[5]
Derivative assets		823	[6]	1,057	[7]
Total assets		34,287		32,872
Liabilities:
Derivative liabilities		602	[8]	666	[9]
Short positions		31	[8]	21	[9]
Total liabilities		633		687
Fair value, recurring | Mortgage Servicing Rights
Assets:
Mortgage Servicing Rights		858
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		514		748
Liabilities:
Derivative liabilities		178		265
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		124		202
Liabilities:
Derivative liabilities		120		204
Equity Contract | Fair value, recurring
Assets:
Derivative assets		20	[6]	0
Liabilities:
Derivative liabilities		137		91
Commodity Contract | Fair value, recurring
Assets:
Derivative assets		165		107
Liabilities:
Derivative liabilities		167		106
U.S. Treasury and federal agencies
Assets:
Available-for-sale securities, fair value		98		549
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value		98		549
Trading securities		12		23
Obligations of states and political subdivisions
Assets:
Available-for-sale securities, fair value		44		45
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value		44		45
Trading securities		22		39
Agency mortgage-backed securities | Residential mortgage-backed securities
Assets:
Available-for-sale securities, fair value	[10]	15,319		15,608
Agency mortgage-backed securities | Residential mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		15,319		15,608
Trading securities		395		8
Agency mortgage-backed securities | Commercial mortgage-backed securities
Assets:
Available-for-sale securities, fair value		10,167		9,055
Agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		10,167		9,055
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Assets:
Available-for-sale securities, fair value		3,293		3,112
Non-agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		3,293		3,112
Asset-backed securities and other debt securities
Assets:
Available-for-sale securities, fair value		2,218		2,116
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		2,218		2,116
Trading securities		63		15
Equity securities
Assets:
Available-for-sale securities, fair value	[11]	681		698
Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		69	[2]	91	[3]
Trading securities		370		325
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale securities, fair value		166	[2],[12]	561	[3],[13]
Trading securities		371	[12]	325	[13]
Derivative assets		40	[6],[12]	42	[7],[13]
Total assets		577	[12]	928	[13]
Liabilities:
Derivative liabilities		39	[8],[12]	30	[9],[13]
Short positions		25	[8],[12]	17	[9],[13]
Total liabilities		64	[12]	47	[13]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		1	[12]	20	[13]
Liabilities:
Derivative liabilities		1	[12]	3	[13]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		39	[12]	22	[13]
Liabilities:
Derivative liabilities		38	[12]	27	[13]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value		98	[12]	471	[13]
Trading securities	[12]	1
Fair Value, Inputs, Level 1 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		68	[2],[12]	90	[3],[13]
Trading securities		370	[12]	325	[13]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale securities, fair value		31,042	[2],[12]	30,015	[3],[13]
Trading securities		491	[12]	85	[13]
Residential mortgage loans held for sale		399	[12]	686
Derivative assets		775	[6],[12]	1,002	[7],[13]
Total assets		32,707	[12]	31,788	[13]
Liabilities:
Derivative liabilities		421	[8],[12]	540	[9],[13]
Short positions		6	[8],[12]	4	[9],[13]
Total liabilities		427	[12]	544	[13]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		505	[12]	715	[13]
Liabilities:
Derivative liabilities		172	[12]	257	[13]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		124	[12]	202	[13]
Liabilities:
Derivative liabilities		120	[12]	204	[13]
Fair Value, Inputs, Level 2 | Equity Contract | Fair value, recurring
Assets:
Derivative assets	[6]	20
Liabilities:
Derivative liabilities		0
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		126	[12]	85	[13]
Liabilities:
Derivative liabilities		129	[12]	79	[13]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value		0	[12]	78	[13]
Trading securities		11	[12]	23	[13]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value		44	[12]	45	[13]
Trading securities		22	[12]	39	[13]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		15,319	[12]	15,608	[13]
Trading securities		395	[12]	8	[13]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		10,167	[12]	9,055	[13]
Fair Value, Inputs, Level 2 | Non-agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		3,293	[12]	3,112	[13]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		2,218	[12]	2,116	[13]
Trading securities		63	[12]	15	[13]
Fair Value, Inputs, Level 2 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		1	[2],[12]	1	[3],[13]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Residential mortgage loans measured at fair value		137	[4]	143	[5]
Derivative assets		8	[6]	13	[7]
Total assets		1,003		156
Liabilities:
Derivative liabilities		142	[8]	96	[9]
Total liabilities		142		96
Fair Value, Inputs, Level 3 | Fair value, recurring | Mortgage Servicing Rights
Assets:
Mortgage Servicing Rights		858
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		8		13
Liabilities:
Derivative liabilities		5		5
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets		0		0
Liabilities:
Derivative liabilities		$ 137		$ 91

[1] Amortized cost of $ 31,644 and $ 31,024 at December 31, 2017 and 2016 , respectively.

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

[3] Excludes FHLB, FRB and DTCC restricted stock holdings totaling $ 248 , $ 358 and $1 , respectively, at December 31, 2016 .

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

[7] Included in other assets in the Consolidated Balance Sheets.

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

[9] Included in other liabilities in the Consolidated Balance Sheet s.

[10] Includes interest-only mortgage-backed securities of $ 34 and $ 60 as of December 31, 2017 and 2016 , respectively, recorded at fair value with fair value changes recorded in securities gains, net , i n the Consolidated Statements of Income .

[11] Equity securities consist of FHLB, FRB and DTCC restricted stock holdings of $ 248 , $ 362 , and $ 2 , respectively, at December 31, 2017 and $ 248 , $ 358 and $ 1 , respectively, at December 31, 2016 , that are carried at cost, and certain mutual fund and equity security holdings.

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

[13] During the year ended December 31, 2016 , no assets or liabilities were transferred between Level 1 and Level 2.