Derivatives (Notional Amounts and Fair Values for All Derivative Instruments Included in the Consolidated Balance Sheets) (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value
Fair value - Derivative Assets	$ 2,179	$ 1,852
Fair value - Derivative Liabilities	979	938
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value
Fair value - Derivative Assets	605	411
Fair value - Derivative Liabilities		2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	492	372
Fair value - Derivative Liabilities		2
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
Fair value - Derivative Assets	492	372
Fair value - Derivative Liabilities		2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging
Derivatives, Fair Value
Fair value - Derivative Assets	113	39
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	113	39
Nondesignated
Derivatives, Fair Value
Fair value - Derivative Assets	1,574	1,441
Fair value - Derivative Liabilities	979	936
Nondesignated | Risk Management and Other Business Purposes
Derivatives, Fair Value
Fair value - Derivative Assets	720	504
Fair value - Derivative Liabilities	191	71
Nondesignated | Risk Management and Other Business Purposes | Interest Rate Contract | Servicing Rights
Derivatives, Fair Value
Notional amount	8,407	11,657
Fair value - Derivative Assets	392	239
Fair value - Derivative Liabilities	73	9
Nondesignated | Risk Management and Other Business Purposes | Forward Contracts | Assets Held For Sale
Derivatives, Fair Value
Notional amount	1,713	1,330
Fair value - Derivative Assets		3
Fair value - Derivative Liabilities	17	1
Nondesignated | Risk Management and Other Business Purposes | Warrant
Derivatives, Fair Value
Notional amount	441	369
Fair value - Derivative Assets	327	262
Nondesignated | Risk Management and Other Business Purposes | Swap
Derivatives, Fair Value
Notional amount	1,236	1,292
Fair value - Derivative Liabilities	99	61
Nondesignated | Risk Management and Other Business Purposes | Foreign Exchange Contract
Derivatives, Fair Value
Notional amount	214
Fair value - Derivative Assets	1
Fair value - Derivative Liabilities	2
Nondesignated | Customer Accommodation
Derivatives, Fair Value
Fair value - Derivative Assets	854	937
Fair value - Derivative Liabilities	788	865
Nondesignated | Customer Accommodation | Interest Rate Contract
Derivatives, Fair Value
Notional amount	31,777	29,889
Fair value - Derivative Assets	405	242
Fair value - Derivative Liabilities	414	249
Nondesignated | Customer Accommodation | Interest Rate Lock Commitments
Derivatives, Fair Value
Notional amount	1,185	721
Fair value - Derivative Assets	34	15
Nondesignated | Customer Accommodation | Commodity Contract
Derivatives, Fair Value
Notional amount	2,091	2,464
Fair value - Derivative Assets	137	294
Fair value - Derivative Liabilities	123	276
Nondesignated | Customer Accommodation | Foreign Exchange Contract
Derivatives, Fair Value
Notional amount	13,745	16,243
Fair value - Derivative Assets	278	386
Fair value - Derivative Liabilities	$ 251	$ 340