Fair Value, Estimates for Financial Instruments Excluding those Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Financial assets
Cash and due from banks		$ 20,880	$ 23,551
Interest-earning deposits with banks		143,547	149,736
Federal funds sold and securities purchased under resale agreements		112,119	80,207
Held-to-maturity debt securities		145,876	144,788
Mortgage loans held for sale	[1]	22,998	15,126
Loans held for sale	[1]	1,181	2,041
Loans	[1]	949,878	953,110
Financial liabilities
Deposits		1,288,426	1,286,170
Short-term borrowings		115,344	105,787
Long-term debt		241,476	229,044
Carrying amount [Member]
Financial assets
Cash and due from banks		20,880	23,551
Interest-earning deposits with banks		143,547	149,736
Federal funds sold and securities purchased under resale agreements		112,119	80,207
Held-to-maturity debt securities		145,876	144,788
Mortgage loans held for sale		6,655	3,355
Loans held for sale		63	572
Loans		920,977	923,703
Nonmarketable equity securities		5,622	5,643
Financial assets fair value disclosure		1,355,739	1,331,555
Financial liabilities
Deposits		139,343	130,645
Short-term borrowings		115,344	105,787
Long-term debt		241,441	229,008
Financial liabilities fair value disclosure		496,128	465,440
Fair Value Disclosures, Textual [Abstract]
Deposit Liabilities With No Defined or Contractual Maturity		1,100,000	1,200,000
Capital lease obligations		35	36
Carrying amount [Member] | Finance leases financing receivable [Member]
Financial assets
Loans		19,000	19,700
Estimated fair value [Member]
Financial assets
Cash and due from banks		20,880	23,551
Interest-earning deposits with banks		143,547	149,736
Federal funds sold and securities purchased under resale agreements		112,119	80,207
Held-to-maturity debt securities		147,864	142,115
Mortgage loans held for sale		7,650	3,362
Loans held for sale		63	572
Loans		928,440	917,915
Nonmarketable equity securities		5,654	5,675
Financial assets fair value disclosure		1,366,217	1,323,133
Financial liabilities
Deposits		139,202	130,089
Short-term borrowings		115,345	105,789
Long-term debt		244,155	228,134
Financial liabilities fair value disclosure		498,702	464,012
Fair Value Disclosures, Textual [Abstract]
Loan commitments and standby, commercial and similar letters of credit		1,000	1,000
Estimated fair value [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and due from banks		20,880	23,551
Interest-earning deposits with banks		143,312	149,542
Federal funds sold and securities purchased under resale agreements		0	0
Held-to-maturity debt securities		45,336	44,339
Mortgage loans held for sale		0	0
Loans held for sale		0	0
Loans		0	0
Nonmarketable equity securities		0	0
Financial assets fair value disclosure		209,528	217,432
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 2 [Member]
Financial assets
Cash and due from banks		0	0
Interest-earning deposits with banks		235	194
Federal funds sold and securities purchased under resale agreements		112,119	80,207
Held-to-maturity debt securities		101,943	97,275
Mortgage loans held for sale		3,548	2,129
Loans held for sale		63	572
Loans		49,839	45,190
Nonmarketable equity securities		0	0
Financial assets fair value disclosure		267,747	225,567
Financial liabilities
Deposits		106,653	107,448
Short-term borrowings		115,345	105,789
Long-term debt		242,529	225,904
Financial liabilities fair value disclosure		464,527	439,141
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 debt securities		585	501
Mortgage loans held for sale		4,102	1,233
Loans held for sale		0	0
Loans		878,601	872,725
Nonmarketable equity securities		5,654	5,675
Financial assets fair value disclosure		888,942	880,134
Financial liabilities
Deposits		32,549	22,641
Short-term borrowings		0	0
Long-term debt		1,626	2,230
Financial liabilities fair value disclosure		$ 34,175	$ 24,871

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