Notional Amounts and Fair Values for All Derivative Instruments Included in the Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	$ 1,852	$ 2,080
Fair value - Derivative Liabilities	938	1,043
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	411	435
Fair value - Derivative Liabilities	2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	372	399
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 [Line Items]
Notional amount	2,705	2,205
Fair value - Derivative Assets	372	399
Fair value - Derivative Liabilities	2
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	39	36
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging | Interest Rate Swap | Commercial and Industrial Loans
Derivatives, Fair Value [Line Items]
Notional amount	5,475	3,150
Fair value - Derivative Assets	39	36
Nondesignated
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	1,441	1,645
Fair value - Derivative Liabilities	936	1,043
Nondesignated | Risk Management and Other Business Purposes
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	504	596
Fair value - Derivative Liabilities	71	55
Nondesignated | Risk Management and Other Business Purposes | Interest Rate Contract | Servicing Rights
Derivatives, Fair Value [Line Items]
Notional amount	11,657	4,487
Fair value - Derivative Assets	239	181
Fair value - Derivative Liabilities	9
Nondesignated | Risk Management and Other Business Purposes | Forward Contracts | Assets Held For Sale | Residential Mortgage
Derivatives, Fair Value [Line Items]
Notional amount	1,330	999
Fair value - Derivative Assets	3
Fair value - Derivative Liabilities	1	6
Nondesignated | Risk Management and Other Business Purposes | Warrant
Derivatives, Fair Value [Line Items]
Notional amount	369	691
Fair value - Derivative Assets	262	415
Nondesignated | Risk Management and Other Business Purposes | Swap
Derivatives, Fair Value [Line Items]
Notional amount	1,292	1,092
Fair value - Derivative Liabilities	61	49
Nondesignated | Customer Accommodation
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	937	1,049
Fair value - Derivative Liabilities	865	988
Nondesignated | Customer Accommodation | Interest Rate Contract
Derivatives, Fair Value [Line Items]
Notional amount	29,889	29,558
Fair value - Derivative Assets	242	272
Fair value - Derivative Liabilities	249	278
Nondesignated | Customer Accommodation | Interest Rate Lock Commitments
Derivatives, Fair Value [Line Items]
Notional amount	721	613
Fair value - Derivative Assets	15	12
Nondesignated | Customer Accommodation | Commodity Contract
Derivatives, Fair Value [Line Items]
Notional amount	2,464	3,558
Fair value - Derivative Assets	294	348
Fair value - Derivative Liabilities	276	338
Nondesignated | Customer Accommodation | Foreign Exchange Contract
Derivatives, Fair Value [Line Items]
Notional amount	16,243	16,475
Fair value - Derivative Assets	386	417
Fair value - Derivative Liabilities	$ 340	$ 372