Branch Assets and Liabilities Held For Sale - Additional Information (Detail) (USD $)	Sep. 30, 2012 Branch	May 31, 2012 Branch	Jul. 31, 2011 Branch
Agreement with First Niagara Bank to sell retail branches			195
Related branch premises, for Percentage of premium of deposits			6.67%
Number of retail branch sold under agreement	57	138
After-tax gain upon closing of transaction, net of allocated non-deductible goodwill	$ 23,000,000	$ 71,000,000
Branch agreement premium Received		886,000,000
Branch agreement deferred premium received		209,000,000
Agreement includes the transfer in deposits		13,200,000,000
Agreement includes the transfer of Loans		$ 2,100,000,000