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Loans And The Allowance For Credit Losses (Loans Modified In Past Twelve Months Which Subsequently Defaulted) (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2012
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification $ 127 $ 269
Commercial And Industrial [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 23 59
Commercial Real Estate Mortgage - Owner Occupied [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 23 34
Commercial Real Estate Construction - Owner Occupied [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification   1
Total Commercial [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 46 94
Commercial Investor Real Estate Mortgage [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 51 111
Commercial Investor Real Estate Construction [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 12 19
Total Investor Real Estate [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 63 130
Residential First Mortgage [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 12 33
Home Equity [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification 6 12
Total Consumer [Member]
    
Financing Receivable, Modifications [Line Items]    
Defaulted during period where modified in a TDR, twelve months prior to modification $ 18 $ 45