Derivatives (Notional Amounts and Fair Values for All Derivative Instruments Included in the Consolidated Balance Sheets) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value
Fair value - Derivative Assets	$ 1,057	$ 1,852
Fair value - Derivative Liabilities	666	938
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Fair value - Derivative Assets	345	411
Fair value - Derivative Liabilities	12	2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	323	372
Fair value - Derivative Liabilities	12	2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging | Interest Rate Swap | Long-Term Debt
Derivatives, Fair Value
Notional amount	3,455	2,705
Fair value - Derivative Assets	323	372
Fair value - Derivative Liabilities	12	2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	22	39
Fair value - Derivative Liabilities	0	0
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging | Interest Rate Swap | Commercial and Industrial Loans
Derivatives, Fair Value
Notional amount	4,475	5,475
Fair value - Derivative Assets	22	39
Fair value - Derivative Liabilities	0	0
Nondesignated
Derivatives, Fair Value
Fair value - Derivative Assets	712	1,441
Fair value - Derivative Liabilities	654	936
Nondesignated | Risk Management and Other Business Purposes
Derivatives, Fair Value
Fair value - Derivative Assets	185	504
Fair value - Derivative Liabilities	133	71
Nondesignated | Risk Management and Other Business Purposes | Interest Rate Contract | Servicing Rights
Derivatives, Fair Value
Notional amount	10,522	11,657
Fair value - Derivative Assets	165	239
Fair value - Derivative Liabilities	39	9
Nondesignated | Risk Management and Other Business Purposes | Forward Contracts | Assets Held For Sale | Residential Mortgage
Derivatives, Fair Value
Notional amount	1,823	1,330
Fair value - Derivative Assets	20	3
Fair value - Derivative Liabilities	3	1
Nondesignated | Risk Management and Other Business Purposes | Warrant
Derivatives, Fair Value
Notional amount		369
Fair value - Derivative Assets		262
Fair value - Derivative Liabilities		0
Nondesignated | Risk Management and Other Business Purposes | Swap
Derivatives, Fair Value
Notional amount	1,300	1,292
Fair value - Derivative Assets	0	0
Fair value - Derivative Liabilities	91	61
Nondesignated | Risk Management and Other Business Purposes | Foreign Exchange Contract
Derivatives, Fair Value
Notional amount	111
Fair value - Derivative Assets	0
Fair value - Derivative Liabilities	0
Nondesignated | Customer Accommodation
Derivatives, Fair Value
Fair value - Derivative Assets	527	937
Fair value - Derivative Liabilities	521	865
Nondesignated | Customer Accommodation | Interest Rate Contract
Derivatives, Fair Value
Notional amount	33,431	29,889
Fair value - Derivative Assets	205	242
Fair value - Derivative Liabilities	210	249
Nondesignated | Customer Accommodation | Interest Rate Lock Commitments
Derivatives, Fair Value
Notional amount	701	721
Fair value - Derivative Assets	13	15
Fair value - Derivative Liabilities	1	0
Nondesignated | Customer Accommodation | Commodity Contract
Derivatives, Fair Value
Notional amount	2,095	2,464
Fair value - Derivative Assets	107	294
Fair value - Derivative Liabilities	106	276
Nondesignated | Customer Accommodation | Foreign Exchange Contract
Derivatives, Fair Value
Notional amount	11,013	16,243
Fair value - Derivative Assets	202	386
Fair value - Derivative Liabilities	$ 204	$ 340