Derivative Financial Instruments - Notional Amounts and Fair Values for All Derivative Instruments Included in the Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value
Derivative Assets	$ 2,757	$ 3,173
Derivative Liabilities	3,300	3,952
Amount of variation margin payment applied to derivative asset contracts	854	1,000
Amount of variation margin payment applied to derivative liability contracts	684	1,000
Designated as Hedging Instrument | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Derivative Assets	178	157
Derivative Liabilities	239	296
Designated as Hedging Instrument | Fair Value Hedging | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Derivative Assets	164	126
Derivative Liabilities	144	195
Designated as Hedging Instrument | Fair Value Hedging | Interest rate swap | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Long-term debt
Derivatives, Fair Value
Notional Amount	5,955	5,955
Derivative Assets	164	126
Derivative Liabilities	144	195
Designated as Hedging Instrument | Cash Flow Hedging | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Derivative Assets	14	31
Derivative Liabilities	95	101
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swap | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Commercial and industrial
Derivatives, Fair Value
Notional Amount	8,000	8,000
Derivative Assets	0	0
Derivative Liabilities	80	76
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swap | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Commercial mortgage and commercial construction
Derivatives, Fair Value
Notional Amount	4,000	4,000
Derivative Assets	0	0
Derivative Liabilities	14	25
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate floor | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Commercial and industrial
Derivatives, Fair Value
Notional Amount	3,000	3,000
Derivative Assets	4	4
Derivative Liabilities	0	0
Designated as Hedging Instrument | Cash Flow Hedging | Forward starting interest rate swap | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Commercial and industrial
Derivatives, Fair Value
Notional Amount	10,000	11,000
Derivative Assets	6	22
Derivative Liabilities	1	0
Designated as Hedging Instrument | Cash Flow Hedging | Forward starting interest rate swap | Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Commercial mortgage and commercial construction
Derivatives, Fair Value
Notional Amount	4,000	4,000
Derivative Assets	4	5
Derivative Liabilities	0	0
Not Designated as Hedging Instrument
Derivatives, Fair Value
Derivative Assets	2,579	3,016
Derivative Liabilities	3,061	3,656
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes
Derivatives, Fair Value
Derivative Assets	76	85
Derivative Liabilities	214	220
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Interest rate contracts related to MSR portfolio
Derivatives, Fair Value
Notional Amount	2,700	2,975
Derivative Assets	61	62
Derivative Liabilities	3	17
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Forward contracts related to residential mortgage loans held for sale | Loans held for sale
Derivatives, Fair Value
Notional Amount	960	1,869
Derivative Assets	1	9
Derivative Liabilities	8	7
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Swap
Derivatives, Fair Value
Notional Amount	3,644	3,358
Derivative Assets	0	0
Derivative Liabilities	192	195
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Foreign exchange contracts
Derivatives, Fair Value
Notional Amount	194	156
Derivative Assets	0	1
Derivative Liabilities	1	0
Not Designated as Hedging Instrument | Risk Management and Other Business Purposes | Interest-only strips
Derivatives, Fair Value
Notional Amount	58	58
Derivative Assets	4	4
Derivative 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	12,000	12,000
Derivative Assets	10	9
Derivative Liabilities	10	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	0	0
Derivative Liabilities	0	0
Not Designated as Hedging Instrument | Customer Accommodation
Derivatives, Fair Value
Derivative Assets	2,503	2,931
Derivative Liabilities	2,847	3,436
Not Designated as Hedging Instrument | Customer Accommodation | Foreign exchange contracts
Derivatives, Fair Value
Notional Amount	24,329	25,322
Derivative Assets	450	453
Derivative Liabilities	406	422
Not Designated as Hedging Instrument | Customer Accommodation | Interest rate contracts
Derivatives, Fair Value
Notional Amount	91,778	83,605
Derivative Assets	893	998
Derivative Liabilities	1,385	1,663
Amount of variation margin payment applied to derivative asset contracts	505	694
Amount of variation margin payment applied to derivative liability contracts	27	37
Not Designated as Hedging Instrument | Customer Accommodation | Interest rate lock commitments
Derivatives, Fair Value
Notional Amount	367	216
Derivative Assets	7	2
Derivative Liabilities	0	1
Not Designated as Hedging Instrument | Customer Accommodation | Commodity contracts
Derivatives, Fair Value
Notional Amount	16,942	16,122
Derivative Assets	1,153	1,478
Derivative Liabilities	1,056	1,350
Not Designated as Hedging Instrument | Customer Accommodation | TBA securities
Derivatives, Fair Value
Notional Amount	34	62
Derivative Assets	0	0
Derivative Liabilities	$ 0	$ 0