Derivatives (Notional Amounts and Fair Values for All Derivative Instruments Included in the Consolidated Balance Sheets) (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value
Fair value - Derivative Assets	$ 780	$ 1,057
Fair value - Derivative Liabilities	491	666
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Fair value - Derivative Assets	317	345
Fair value - Derivative Liabilities	18	12
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	317	323
Fair value - Derivative Liabilities	5	12
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging | Interest Rate Swap | Long-Term Debt
Derivatives, Fair Value
Notional amount	2,955	3,455
Fair value - Derivative Assets	317	323
Fair value - Derivative Liabilities	5	12
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	0	22
Fair value - Derivative Liabilities	13	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	4,475
Fair value - Derivative Assets	0	22
Fair value - Derivative Liabilities	13	0
Nondesignated
Derivatives, Fair Value
Fair value - Derivative Assets	463	712
Fair value - Derivative Liabilities	473	654
Nondesignated | Risk Management and Other Business Purposes
Derivatives, Fair Value
Fair value - Derivative Assets	62	185
Fair value - Derivative Liabilities	124	133
Nondesignated | Risk Management and Other Business Purposes | Interest Rate Contract | Servicing Rights
Derivatives, Fair Value
Notional amount	11,602	10,522
Fair value - Derivative Assets	59	165
Fair value - Derivative Liabilities	18	39
Nondesignated | Risk Management and Other Business Purposes | Forward Contracts | Assets Held For Sale
Derivatives, Fair Value
Notional amount	1,749	1,823
Fair value - Derivative Assets	3	20
Fair value - Derivative Liabilities	3	3
Nondesignated | Risk Management and Other Business Purposes | Swap
Derivatives, Fair Value
Notional amount	1,563	1,300
Fair value - Derivative Assets	0	0
Fair value - Derivative Liabilities	98	91
Nondesignated | Risk Management and Other Business Purposes | Foreign Exchange Contract
Derivatives, Fair Value
Notional amount	194	111
Fair value - Derivative Assets	0	0
Fair value - Derivative Liabilities	5	0
Nondesignated | Customer Accommodation
Derivatives, Fair Value
Fair value - Derivative Assets	401	527
Fair value - Derivative Liabilities	349	521
Nondesignated | Customer Accommodation | Interest Rate Contract
Derivatives, Fair Value
Notional amount	39,933	33,431
Fair value - Derivative Assets	179	205
Fair value - Derivative Liabilities	130	210
Nondesignated | Customer Accommodation | Interest Rate Lock Commitments
Derivatives, Fair Value
Notional amount	769	701
Fair value - Derivative Assets	14	13
Fair value - Derivative Liabilities	0	1
Nondesignated | Customer Accommodation | Commodity Contract
Derivatives, Fair Value
Notional amount	2,382	2,095
Fair value - Derivative Assets	90	107
Fair value - Derivative Liabilities	91	106
Nondesignated | Customer Accommodation | TBAs
Derivatives, Fair Value
Notional amount	56
Fair value - Derivative Assets	0
Fair value - Derivative Liabilities	0
Nondesignated | Customer Accommodation | Foreign Exchange Contract
Derivatives, Fair Value
Notional amount	10,653	11,013
Fair value - Derivative Assets	118	202
Fair value - Derivative Liabilities	$ 128	$ 204