Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Assets:
Available-for-sale debt securities, fair value	[1]	$ 32,830	$ 31,751
Trading debt securities		287	492
Equity securities		452	439
Loans measured at FV		179	137
Loans held for sale measured at FV		537	399
Derivative assets		1,114	823
Total assets		249	1,548
Commercial
Assets:
Loans held for sale measured at FV		7	0
Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		32,278	31,139
Trading debt securities		287	492
Equity securities		452	439
Residential mortgage loans held for sale		537	399
Mortgage Servicing Rights		938	858
Derivative assets		1,114	823
Total assets		35,792	34,287
Liabilities:
Derivative liabilities		874	602
Short positions		138	31
Total liabilities		1,012	633
Fair value, recurring | Commercial
Assets:
Loans held for sale measured at FV		7
Fair value, recurring | Residential Mortgage Loans
Assets:
Loans measured at FV		179	137
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		655	514
Liabilities:
Derivative liabilities		329	178
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		152	124
Liabilities:
Derivative liabilities		142	120
Equity Contract | Fair value, recurring
Assets:
Derivative assets			20
Liabilities:
Derivative liabilities		125	137
Commodity Contract | Fair value, recurring
Assets:
Derivative assets		307	165
Liabilities:
Derivative liabilities		278	167
U.S. Treasury and federal agencies
Assets:
Available-for-sale debt securities, fair value		97	98
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		97	98
Trading debt securities		16	12
Obligations of states and political subdivisions
Assets:
Available-for-sale debt securities, fair value		2	44
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		2	44
Trading debt securities		35	22
Agency mortgage-backed securities | Residential mortgage-backed securities
Assets:
Available-for-sale debt securities, fair value	[2]	16,247	15,319
Agency mortgage-backed securities | Residential mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		16,247	15,319
Trading debt securities		68	395
Agency mortgage-backed securities | Commercial mortgage-backed securities
Assets:
Available-for-sale debt securities, fair value		10,650	10,167
Agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		10,650	10,167
Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Assets:
Available-for-sale debt securities, fair value		3,267	3,293
Non-agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		3,267	3,293
Asset-backed securities and other debt securities
Assets:
Available-for-sale debt securities, fair value		2,015	2,218
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		2,015	2,218
Trading debt securities		168	63
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		97	98
Trading debt securities		0	1
Equity securities		452	438
Residential mortgage loans held for sale		0	0
Mortgage Servicing Rights		0	0
Derivative assets		93	40
Total assets		642	577
Liabilities:
Derivative liabilities		27	39
Short positions		110	25
Total liabilities		137	64
Fair Value, Inputs, Level 1 | Fair value, recurring | Commercial
Assets:
Loans held for sale measured at FV		0
Fair Value, Inputs, Level 1 | Fair value, recurring | Residential Mortgage Loans
Assets:
Loans measured at FV		0	0
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		0	1
Liabilities:
Derivative liabilities		8	1
Fair Value, Inputs, Level 1 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		0	0
Fair Value, Inputs, Level 1 | Equity Contract | Fair value, recurring
Assets:
Derivative assets			0
Liabilities:
Derivative liabilities		0	0
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		93	39
Liabilities:
Derivative liabilities		19	38
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		97	98
Trading debt securities		0	1
Fair Value, Inputs, Level 1 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Fair Value, Inputs, Level 1 | Agency mortgage-backed securities | Residential mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Fair Value, Inputs, Level 1 | Agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Fair Value, Inputs, Level 1 | Non-agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Fair Value, Inputs, Level 1 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Fair Value, Inputs, Level 2
Assets:
Total assets		67
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		32,181	31,041
Trading debt securities		287	491
Equity securities		0	1
Residential mortgage loans held for sale		537	399
Mortgage Servicing Rights		0	0
Derivative assets		1,014	775
Total assets		34,026	32,707
Liabilities:
Derivative liabilities		714	421
Short positions		28	6
Total liabilities		742	427
Fair Value, Inputs, Level 2 | Fair value, recurring | Commercial
Assets:
Loans held for sale measured at FV		7
Fair Value, Inputs, Level 2 | Fair value, recurring | Residential Mortgage Loans
Assets:
Loans measured at FV		0	0
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		648	505
Liabilities:
Derivative liabilities		313	172
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		152	124
Liabilities:
Derivative liabilities		142	120
Fair Value, Inputs, Level 2 | Equity Contract | Fair value, recurring
Assets:
Derivative assets			20
Liabilities:
Derivative liabilities		0	0
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		214	126
Liabilities:
Derivative liabilities		259	129
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		16	11
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		2	44
Trading debt securities		35	22
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		16,247	15,319
Trading debt securities		68	395
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		10,650	10,167
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		3,267	3,293
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		2,015	2,218
Trading debt securities		168	63
Fair Value, Inputs, Level 3
Assets:
Total assets		182	1,548
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Equity securities		0	0
Residential mortgage loans held for sale		0	0
Mortgage Servicing Rights		938	858
Derivative assets		7	8
Total assets		1,124	1,003
Liabilities:
Derivative liabilities		133	142
Short positions		0	0
Total liabilities		133	142
Fair Value, Inputs, Level 3 | Fair value, recurring | Commercial
Assets:
Loans held for sale measured at FV		0
Fair Value, Inputs, Level 3 | Fair value, recurring | Residential Mortgage Loans
Assets:
Loans measured at FV		179	137
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		7	8
Liabilities:
Derivative liabilities		8	5
Fair Value, Inputs, Level 3 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		0	0
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets			0
Liabilities:
Derivative liabilities		125	137
Fair Value, Inputs, Level 3 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		0	0
Fair Value, Inputs, Level 3 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Fair Value, Inputs, Level 3 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Fair Value, Inputs, Level 3 | Agency mortgage-backed securities | Residential mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		0	0
Fair Value, Inputs, Level 3 | Agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Fair Value, Inputs, Level 3 | Non-agency mortgage-backed securities | Commercial mortgage-backed securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Fair Value, Inputs, Level 3 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale debt securities, fair value		0	0
Trading debt securities		$ 0	$ 0

[1] Amortized cost of $ 33,128 and $ 31,577 at December 31, 2018 and 2017 , respectively.

[2] Includes interest-only mortgage-backed securities of $ 0 and $ 34 as of December 31, 2018 and 2017 , respectively, recorded at fair value with fair value changes recorded in securities (losses) gains, net , i n the Consolidated Statements of Income .