Derivatives (Notional Amounts and Fair Values for All Derivative Instruments Included in the Condensed Consolidated Balance Sheets) (Detail) - USD ($) $ in Millions	Mar. 31, 2020		Dec. 31, 2019
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	$ 4,100		$ 1,673
Derivative Liability, Fair Value, Gross Liability	1,866		741
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	888		508
Derivative Liability, Fair Value, Gross Liability	8		2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	616		393
Derivative Liability, Fair Value, Gross Liability	0		0
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging | Interest Rate Swap | Long-term debt
Derivatives, Fair Value
Notional Amount	2,705		2,705
Derivative Asset, Fair Value, Gross Asset	616		393
Derivative Liability, Fair Value, Gross Liability	0		0
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	272		115
Derivative Liability, Fair Value, Gross Liability	8		2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging | Interest Rate Swap | Commercial and Industrial Loans
Derivatives, Fair Value
Notional Amount	8,000		8,000
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	8		2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging | Interest Rate Floor | Commercial and Industrial Loans
Derivatives, Fair Value
Notional Amount	3,000		3,000
Derivative Asset, Fair Value, Gross Asset	272		115
Derivative Liability, Fair Value, Gross Liability	0		0
Nondesignated
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	3,212		1,165
Derivative Liability, Fair Value, Gross Liability	1,858		739
Nondesignated | Risk Management And Other Business Purposes
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	307		132
Derivative Liability, Fair Value, Gross Liability	248		175
Nondesignated | Risk Management And Other Business Purposes | Interest Rate Contract | Mortgage Servicing Rights
Derivatives, Fair Value
Notional Amount	6,220		6,420
Derivative Asset, Fair Value, Gross Asset	287		131
Derivative Liability, Fair Value, Gross Liability	4		2
Nondesignated | Risk Management And Other Business Purposes | Forward Contracts Related to Residential Mortgage LoansHeld for Sale | Loans Held For Sale
Derivatives, Fair Value
Notional Amount	3,987		2,901
Derivative Asset, Fair Value, Gross Asset	11		1
Derivative Liability, Fair Value, Gross Liability	72		5
Nondesignated | Risk Management And Other Business Purposes | Swap
Derivatives, Fair Value
Notional Amount	2,643		3,082
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	171		163
Nondesignated | Risk Management And Other Business Purposes | Foreign Exchange Contract
Derivatives, Fair Value
Notional Amount	198		195
Derivative Asset, Fair Value, Gross Asset	8		0
Derivative Liability, Fair Value, Gross Liability	0		5
Nondesignated | Risk Management And Other Business Purposes | Commercial loan trading
Derivatives, Fair Value
Notional Amount	21
Derivative Asset, Fair Value, Gross Asset	1
Derivative Liability, Fair Value, Gross Liability	1
Nondesignated | Customer Accommodation
Derivatives, Fair Value
Derivative Asset, Fair Value, Gross Asset	2,905		1,033
Derivative Liability, Fair Value, Gross Liability	1,610		564
Nondesignated | Customer Accommodation | Interest Rate Contract
Derivatives, Fair Value
Notional Amount	76,134	[1]	73,327	[2]
Derivative Asset, Fair Value, Gross Asset	1,483	[1]	579	[2]
Derivative Liability, Fair Value, Gross Liability	299	[1]	148	[2]
Nondesignated | Customer Accommodation | Interest Rate Lock Commitments
Derivatives, Fair Value
Notional Amount	1,941		907
Derivative Asset, Fair Value, Gross Asset	69		18
Derivative Liability, Fair Value, Gross Liability	0		0
Nondesignated | Customer Accommodation | Commodity Contract
Derivatives, Fair Value
Notional Amount	8,209		8,525
Derivative Asset, Fair Value, Gross Asset	1,016		271
Derivative Liability, Fair Value, Gross Liability	1,020		270
Nondesignated | Customer Accommodation | TBA Securities
Derivatives, Fair Value
Notional Amount	22		50
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	0		0
Nondesignated | Customer Accommodation | Foreign Exchange Contract
Derivatives, Fair Value
Notional Amount	13,892		14,144
Derivative Asset, Fair Value, Gross Asset	337		165
Derivative Liability, Fair Value, Gross Liability	$ 291		$ 146

[1] Derivative assets and liabilities are presented net of variation margin of $50 and $1,288, respectively.

[2] Derivative assets and liabilities are presented net of variation margin of $40 and $493, respectively.