Derivative Financial Instruments - Notional Amounts and Fair Values for All Derivative Instruments Included in the Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value
Derivative assets, fair value, gross assets	$ 2,672	$ 3,171
Derivative liabilities, fair value, gross liabilities	2,999	3,951
Derivative assets	2,677	3,173
Derivative liabilities	2,999	3,952
Amount of variation margin payment applied to derivative asset contracts	587	1,000
Amount of variation margin payment applied to derivative liability contracts	721	1,000
Designated as Hedging Instrument
Derivatives, Fair Value
Derivative assets, fair value, gross assets	10	157
Derivative liabilities, fair value, gross liabilities	45	296
Designated as Hedging Instrument | Fair Value Hedging
Derivatives, Fair Value
Derivative assets, fair value, gross assets	0	126
Derivative liabilities, fair value, gross liabilities	32	195
Designated as Hedging Instrument | Fair Value Hedging | Interest rate swaps | Long-term debt
Derivatives, Fair Value
Notional Amount	5,955	5,955
Derivative assets, fair value, gross assets	0	126
Derivative liabilities, fair value, gross liabilities	32	195
Designated as Hedging Instrument | Cash Flow Hedging
Derivatives, Fair Value
Derivative assets, fair value, gross assets	10	31
Derivative liabilities, fair value, gross liabilities	13	101
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swaps | Commercial and Industrial
Derivatives, Fair Value
Notional Amount	8,000	8,000
Derivative assets, fair value, gross assets	2	0
Derivative liabilities, fair value, gross liabilities	11	76
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swaps | Commercial Mortgage and Commercial Construction
Derivatives, Fair Value
Notional Amount		4,000
Derivative assets, fair value, gross assets		0
Derivative liabilities, fair value, gross liabilities		25
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate floors | Commercial and Industrial
Derivatives, Fair Value
Notional Amount	3,000	3,000
Derivative assets, fair value, gross assets	1	4
Derivative liabilities, fair value, gross liabilities	0	0
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swap - forward starting | Commercial and Industrial
Derivatives, Fair Value
Notional Amount	6,000	11,000
Derivative assets, fair value, gross assets	6	22
Derivative liabilities, fair value, gross liabilities	1	0
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swap - forward starting | Commercial Mortgage and Commercial Construction
Derivatives, Fair Value
Notional Amount	4,000	4,000
Derivative assets, fair value, gross assets	1	5
Derivative liabilities, fair value, gross liabilities	1	0
Not Designated as Hedging Instrument
Derivatives, Fair Value
Derivative assets	2,667	3,016
Derivative liabilities	2,954	3,656
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes
Derivatives, Fair Value
Derivative assets, fair value, gross assets	83	85
Derivative liabilities, fair value, gross liabilities	178	220
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Interest rate contracts related to MSR portfolio
Derivatives, Fair Value
Notional Amount	3,205	2,975
Derivative assets, fair value, gross assets	81	62
Derivative liabilities, fair value, gross liabilities	0	17
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Forward contracts related to residential mortgage loans measured at fair value | Loans Measured At Fair Value
Derivatives, Fair Value
Notional Amount	650
Derivative assets, fair value, gross assets	0
Derivative liabilities, fair value, gross liabilities	5
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Forward contracts related to residential mortgage loans measured at fair value | Loans held for sale
Derivatives, Fair Value
Notional Amount		1,869
Derivative assets, fair value, gross assets		9
Derivative liabilities, fair value, gross liabilities		7
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Swap associated with the sale of Visa, Inc. Class B Shares
Derivatives, Fair Value
Notional Amount	4,178	3,358
Derivative assets, fair value, gross assets	0	0
Derivative liabilities, fair value, gross liabilities	168	195
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Foreign exchange contracts
Derivatives, Fair Value
Notional Amount	190	156
Derivative assets, fair value, gross assets	0	1
Derivative liabilities, fair value, gross liabilities	4	0
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Interest-only strips
Derivatives, Fair Value
Notional Amount	39	58
Derivative assets, fair value, gross assets	1	4
Derivative liabilities, fair value, gross liabilities	0	0
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Interest rate contracts for collateral management
Derivatives, Fair Value
Notional Amount	5,000	12,000
Derivative assets, fair value, gross assets	1	9
Derivative liabilities, fair value, gross liabilities	1	1
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Interest rate contracts for LIBOR transition
Derivatives, Fair Value
Notional Amount	597	597
Derivative assets, fair value, gross assets	0	0
Derivative liabilities, fair value, gross liabilities	0	0
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Other
Derivatives, Fair Value
Notional Amount	30
Derivative assets, fair value, gross assets	0
Derivative liabilities, fair value, gross liabilities	0
Not Designated as Hedging Instrument | Customer Accommodation
Derivatives, Fair Value
Derivative assets	2,584	2,931
Derivative liabilities	2,776	3,436
Not Designated as Hedging Instrument | Customer Accommodation | Foreign exchange contracts
Derivatives, Fair Value
Notional Amount	37,734	25,322
Derivative assets, fair value, gross assets	643	453
Derivative liabilities, fair value, gross liabilities	596	422
Not Designated as Hedging Instrument | Customer Accommodation | Interest rate contracts for LIBOR transition
Derivatives, Fair Value
Notional Amount	675
Not Designated as Hedging Instrument | Customer Accommodation | Interest rate contracts
Derivatives, Fair Value
Notional Amount	95,079	83,605
Derivative assets, fair value, gross assets	885	998
Derivative liabilities, fair value, gross liabilities	1,162	1,663
Amount of variation margin payment applied to derivative asset contracts	335	694
Amount of variation margin payment applied to derivative liability contracts	58	37
Not Designated as Hedging Instrument | Customer Accommodation | Interest rate lock commitments
Derivatives, Fair Value
Notional Amount	252	216
Derivative assets, fair value, gross assets	5	2
Derivative liabilities, fair value, gross liabilities	0	1
Not Designated as Hedging Instrument | Customer Accommodation | Commodity contracts
Derivatives, Fair Value
Notional Amount	17,621	16,122
Derivative assets, fair value, gross assets	1,051	1,478
Derivative liabilities, fair value, gross liabilities	1,018	1,350
Not Designated as Hedging Instrument | Customer Accommodation | TBA securities
Derivatives, Fair Value
Notional Amount	27	62
Derivative assets, fair value, gross assets	0	0
Derivative liabilities, fair value, gross liabilities	$ 0	$ 0