Derivative Financial Instruments - Classifications and Hedging Relationships (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	$ 325,969	$ 315,873
Fair Value, Gain	7,471	4,260
Gross amount	(3,942)	(3,336)
Derivative Asset [Abstract]
Amounts subject to master netting arrangements	(1,988)	(1,708)
Cash collateral (received) posted for amounts subject to master netting arrangements	(1,443)	(499)
Net Amount Presented in the Consolidated Balance Sheets	4,040	2,053
Derivative Liability [Abstract]
Amounts subject to master netting arrangements	1,988	1,708
Cash collateral (received) posted for amounts subject to master netting arrangements	1,190	1,262
Net amount	(764)	(366)
Fair value hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	27,152	27,152
Fair Value, Gain	577	113
Gross amount	(5)	(27)
Fair value hedges | Interest rate contracts | Swap | Long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	23,701	23,701
Fair Value, Gain	577	113
Gross amount	0	(25)
Fair value hedges | Interest rate contracts | Swap | Commercial Loan [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	44	44
Fair Value, Gain	0	0
Gross amount	0	0
Fair value hedges | Interest rate contracts | Options | Long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	3,407	3,407
Fair Value, Gain	0	0
Gross amount	(5)	(2)
Not designated as hedges
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	298,817	288,721
Fair Value, Gain	6,894	4,147
Gross amount	(3,937)	(3,309)
Not designated as hedges | Client-related and other risk management
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	254,600	244,317
Fair Value, Gain	6,640	4,077
Gross amount	(3,618)	(3,282)
Not designated as hedges | Client-related and other risk management | Interest rate contracts | Swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	150,165	144,473
Fair Value, Gain	4,029	1,817
Gross amount	(1,026)	(673)
Not designated as hedges | Client-related and other risk management | Interest rate contracts | Options
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	24,997	25,938
Fair Value, Gain	59	28
Gross amount	(23)	(19)
Not designated as hedges | Client-related and other risk management | Interest rate contracts | Forward commitments
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	10,902	7,907
Fair Value, Gain	140	6
Gross amount	(147)	(7)
Not designated as hedges | Client-related and other risk management | Interest rate contracts | Other
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	2,483	1,807
Fair Value, Gain	0	0
Gross amount	0	0
Not designated as hedges | Client-related and other risk management | Equity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	39,452	38,426
Fair Value, Gain	1,483	1,988
Gross amount	(1,781)	(2,307)
Not designated as hedges | Client-related and other risk management | Credit Contract | Other
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	677	0
Fair Value, Gain	5	0
Gross amount	(5)	0
Not designated as hedges | Client-related and other risk management | Credit Contract | Loans and leases
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	1,179	894
Fair Value, Gain	18	0
Gross amount	(22)	(34)
Not designated as hedges | Client-related and other risk management | Credit Contract | Risk participation agreements
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	6,829	6,696
Fair Value, Gain	0	0
Gross amount	(9)	(2)
Not designated as hedges | Client-related and other risk management | Credit Contract | Total Return Swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	1,924	2,531
Fair Value, Gain	318	27
Gross amount	(4)	(11)
Not designated as hedges | Client-related and other risk management | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	13,192	12,986
Fair Value, Gain	242	144
Gross amount	(259)	(164)
Not designated as hedges | Client-related and other risk management | Commodity Contract
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	2,800	2,659
Fair Value, Gain	346	67
Gross amount	(342)	(65)
Not designated as hedges | Mortgage banking | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	19,428	17,562
Fair Value, Gain	210	46
Gross amount	(246)	(20)
Not designated as hedges | Mortgage banking | Interest rate contracts | Swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	300	535
Fair Value, Gain	0	0
Gross amount	0	0
Not designated as hedges | Mortgage banking | Interest rate contracts | Other
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	668	603
Fair Value, Gain	6	2
Gross amount	0	0
Not designated as hedges | Mortgage banking | Interest rate contracts | Interest rate lock commitments
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	7,605	4,427
Fair Value, Gain	177	34
Gross amount	(22)	(2)
Not designated as hedges | Mortgage banking | Interest rate contracts | When issued securities, forward rate agreements and forward commitments
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	10,855	11,997
Fair Value, Gain	27	10
Gross amount	(224)	(18)
Not designated as hedges | MSRs | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	24,789	26,842
Fair Value, Gain	44	24
Gross amount	(73)	(7)
Not designated as hedges | MSRs | Interest rate contracts | Swap
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	21,142	19,196
Fair Value, Gain	0	0
Gross amount	0	0
Not designated as hedges | MSRs | Interest rate contracts | Options
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	1,684	1,519
Fair Value, Gain	15	22
Gross amount	(19)	(2)
Not designated as hedges | MSRs | Interest rate contracts | Other
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	739	567
Fair Value, Gain	0	0
Gross amount	0	0
Not designated as hedges | MSRs | Interest rate contracts | When issued securities, forward rate agreements and forward commitments
Derivative Instruments, Gain (Loss) [Line Items]
Notional Amount	1,224	5,560
Fair Value, Gain	29	2
Gross amount	$ (54)	$ (5)