Fair Value, Estimates for Financial Instruments Excluding those Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Financial assets
Cash and due from banks		$ 22,738	$ 21,757
Interest-earning deposits with banks		128,071	119,493
Federal funds sold and securities purchased under resale agreements		86,465	102,140
Held-to-maturity, amortized cost, net		169,909	153,933	[1]
Loans, net		998,580	952,714
Financial liabilities
Deposits		1,376,532	1,322,626
Short-term borrowings		92,289	104,512
Long-term debt		237,342	228,191
Mortgage loans [Member]
Financial assets
Loans held for sale	[2]	21,795	23,342
Loans, excluding mortgage loans [Member]
Financial assets
Loans held for sale	[2]	1,883	977
Carrying amount [Member]
Financial assets
Cash and due from banks		22,738	21,757
Interest-earning deposits with banks		128,071	119,493
Federal funds sold and securities purchased under resale agreements		86,465	102,140
Held-to-maturity, amortized cost, net		169,909	153,933
Loans, net		979,449	933,042
Nonmarketable equity securities		4,512	4,790
Financial assets fair value disclosure		1,396,484	1,341,896
Financial liabilities
Deposits		110,841	118,849
Short-term borrowings		92,289	104,512
Long-term debt		237,311	228,159
Financial liabilities fair value disclosure		440,441	451,520
Fair Value Disclosures, Textual [Abstract]
Deposit liabilities with no defined or contractual maturity		1,300,000	1,200,000
Carrying amount [Member] | Finance leases [Member]
Financial liabilities
Long-term debt		31	32
Carrying amount [Member] | Mortgage loans [Member]
Financial assets
Loans held for sale		5,130	6,736
Carrying amount [Member] | Loans, excluding mortgage loans [Member]
Financial assets
Loans held for sale		210	5
Carrying amount [Member] | Commercial lease financing receivable [Member]
Financial assets
Loans, net		19,000	19,500
Estimated fair value [Member]
Financial assets
Cash and due from banks		22,738	21,757
Interest-earning deposits with banks		128,071	119,493
Federal funds sold and securities purchased under resale agreements		86,465	102,140
Held-to-maturity, amortized cost, net		177,562	156,860
Loans, net		976,422	945,839
Nonmarketable equity securities		4,548	4,823
Financial assets fair value disclosure		1,401,693	1,358,577
Financial liabilities
Deposits		111,297	119,137
Short-term borrowings		92,289	104,513
Long-term debt		228,215	233,052
Financial liabilities fair value disclosure		431,801	456,702
Fair Value Disclosures, Textual [Abstract]
Loan commitments and standby, commercial and similar letters of credit		853	1,000
Estimated fair value [Member] | Mortgage loans [Member]
Financial assets
Loans held for sale		5,677	7,660
Estimated fair value [Member] | Loans, excluding mortgage loans [Member]
Financial assets
Loans held for sale		210	5
Estimated fair value [Member] | Fair value, inputs, level 1 [Member]
Financial assets
Cash and due from banks		22,738	21,757
Interest-earning deposits with banks		127,831	119,257
Federal funds sold and securities purchased under resale agreements		0	0
Held-to-maturity, amortized cost, net		50,691	46,138
Loans, net		0	0
Nonmarketable equity securities		0	0
Financial assets fair value disclosure		201,260	187,152
Financial liabilities
Deposits		0	0
Short-term borrowings		0	0
Long-term debt		0	0
Financial liabilities fair value disclosure		0	0
Estimated fair value [Member] | Fair value, inputs, level 1 [Member] | Mortgage loans [Member]
Financial assets
Loans held for sale		0	0
Estimated fair value [Member] | Fair value, inputs, level 1 [Member] | Loans, excluding mortgage loans [Member]
Financial assets
Loans held for sale		0	0
Estimated fair value [Member] | Fair value, inputs, level 2 [Member]
Financial assets
Cash and due from banks		0	0
Interest-earning deposits with banks		240	236
Federal funds sold and securities purchased under resale agreements		86,465	102,140
Held-to-maturity, amortized cost, net		126,030	109,933
Loans, net		53,806	54,125
Nonmarketable equity securities		0	0
Financial assets fair value disclosure		269,036	269,378
Financial liabilities
Deposits		82,565	87,279
Short-term borrowings		92,289	104,513
Long-term debt		226,294	231,332
Financial liabilities fair value disclosure		401,148	423,124
Estimated fair value [Member] | Fair value, inputs, level 2 [Member] | Mortgage loans [Member]
Financial assets
Loans held for sale		2,285	2,939
Estimated fair value [Member] | Fair value, inputs, level 2 [Member] | Loans, excluding mortgage loans [Member]
Financial assets
Loans held for sale		210	5
Estimated fair value [Member] | Fair value, inputs, level 3 [Member]
Financial assets
Cash and due from banks		0	0
Interest-earning deposits with banks		0	0
Federal funds sold and securities purchased under resale agreements		0	0
Held-to-maturity, amortized cost, net		841	789
Loans, net		922,616	891,714
Nonmarketable equity securities		4,548	4,823
Financial assets fair value disclosure		931,397	902,047
Financial liabilities
Deposits		28,732	31,858
Short-term borrowings		0	0
Long-term debt		1,921	1,720
Financial liabilities fair value disclosure		30,653	33,578
Estimated fair value [Member] | Fair value, inputs, level 3 [Member] | Mortgage loans [Member]
Financial assets
Loans held for sale		3,392	4,721
Estimated fair value [Member] | Fair value, inputs, level 3 [Member] | Loans, excluding mortgage loans [Member]
Financial assets
Loans held for sale		$ 0	$ 0

[1] (1) Prior to our adoption of CECL on January 1, 2020, the allowance for credit losses (ACL) related to available-for-sale (AFS) and held-to-maturity (HTM) debt securities was not applicable and is therefore presented as $0 at December 31, 2019. For more information, see Note 1 (Summary of Significant Accounting Policies) to Financial Statements in this Report.

[2] (2) Parenthetical amounts represent assets and liabilities that we are required to carry at fair value or have elected the fair value option.