Notional Amounts and Fair Values for All Derivative Instruments Included in the Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	$ 2,552	$ 2,080
Fair value - Derivative Liabilities	1,145	1,043
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	508	435
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	414	399
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	414	399
Accumulated Net Gain (Loss) from Designated or Qualifying Hedges | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	94	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	94	36
Nondesignated
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	2,044	1,645
Fair value - Derivative Liabilities	1,145	1,043
Nondesignated | Risk Management and Other Business Purposes
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	925	596
Fair value - Derivative Liabilities	102	55
Nondesignated | Risk Management and Other Business Purposes | Interest Rate Contract | Servicing Rights
Derivatives, Fair Value [Line Items]
Notional amount	7,657	4,487
Fair value - Derivative Assets	294	181
Fair value - Derivative Liabilities	34
Nondesignated | Risk Management and Other Business Purposes | Forward Contracts | Assets Held For Sale
Derivatives, Fair Value [Line Items]
Notional amount	1,392	999
Fair value - Derivative Assets	1
Fair value - Derivative Liabilities	10	6
Nondesignated | Risk Management and Other Business Purposes | Warrant
Derivatives, Fair Value [Line Items]
Notional amount	915	691
Fair value - Derivative Assets	630	415
Nondesignated | Risk Management and Other Business Purposes | Swap
Derivatives, Fair Value [Line Items]
Notional amount	1,161	1,092
Fair value - Derivative Liabilities	58	49
Nondesignated | Customer Accommodation
Derivatives, Fair Value [Line Items]
Fair value - Derivative Assets	1,119	1,049
Fair value - Derivative Liabilities	1,043	988
Nondesignated | Customer Accommodation | Interest Rate Contract
Derivatives, Fair Value [Line Items]
Notional amount	29,480	29,558
Fair value - Derivative Assets	327	272
Fair value - Derivative Liabilities	335	278
Nondesignated | Customer Accommodation | Interest Rate Lock Commitments
Derivatives, Fair Value [Line Items]
Notional amount	831	613
Fair value - Derivative Assets	19	12
Nondesignated | Customer Accommodation | Commodity Contract
Derivatives, Fair Value [Line Items]
Notional amount	3,121	3,558
Fair value - Derivative Assets	309	348
Fair value - Derivative Liabilities	299	338
Nondesignated | Customer Accommodation | Foreign Exchange Contract
Derivatives, Fair Value [Line Items]
Notional amount	18,500	16,745
Fair value - Derivative Assets	464	417
Fair value - Derivative Liabilities	$ 409	$ 372