Loans and Allowance for Credit Losses (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012	Dec. 31, 2011
Loans and Allowance for Credit Losses (Textual) [Abstract]
Loans pledged at the Federal Home Loan Bank ("FHLB")	$ 71,500,000,000		$ 71,500,000,000			$ 67,000,000,000
Loans pledged at the Federal Reserve Bank	47,700,000,000		47,700,000,000			47,200,000,000
Unearned interest and deferred fees and costs on loans	900,000,000		900,000,000			1,100,000,000
Purchased impaired loans nonperforming assets	100,000,000		100,000,000			200,000,000
Fair value of impaired loans acquired in BankEast transaction					28,000,000
Receivables of impaired loans acquired in BankEast transaction					63,000,000
Cash Receivables of impaired loans acquired in BankEast transaction to be collected with interest					41,000,000
Fair value of non-impaired loans acquired in BankEast transaction					96,000,000
Receivables of Non-Impaired Loans Acquired in BankEast transaction					135,000,000
Cash Receivables of non-impaired loans acquired in BankEast transaction not expected to be collected					22,000,000
Period of accruing loans related nonperforming assets and related ratios			90 days
Extension included in Commercial Real Estate Modifications			up to 12 Months
Partial charge off period of loans secured by 1-4 family properties			180 days
Charge off period of revolving consumer lines and credit cards			180 days
Charge off period of closed-end consumer loans, other than loans secured by 1-4 family properties			120 days
Net gains on the sale of loan	292,000,000	51,000,000	579,000,000	266,000,000
Minimum amount of loans for which allowance recorded for impaired purposes.			5,000,000
Period for capturing full economic cycle in evaluation			11 years
Outstanding balance of loans where trial period was unsuccessful and no longer eligible for a permanent modification	31,000,000
Loans purchased from GNMA [Member]
Additional loans and allowance for credit losses (Textual) [Abstract]
Number of loans in trial period	1,435		1,435
Outstanding balance of loans in trial period	179,000,000		179,000,000
Estimated post-modification balance of loans in trial period	186,000,000		186,000,000
Residential Mortgage [Member]
Additional loans and allowance for credit losses (Textual) [Abstract]
Number of loans in trial period	170		170
Outstanding balance of loans in trial period	26,000,000		26,000,000
Estimated post-modification balance of loans in trial period	28,000,000		28,000,000
Government National Mortgage Association [Member]
Additional loans and allowance for credit losses (Textual) [Abstract]
Loans 30-89 days past due purchased from Government National Mortgage Association mortgage pools whose payments are insured by the Federal Housing Administration and classified as current	427,000,000		427,000,000			545,000,000
Loans 90 days or more past due purchased from Government National Mortgage Association mortgage pools whose payments are insured by the Federal Housing Administration and classified as current	2,900,000,000		2,900,000,000			2,600,000,000
Number of residential mortgage loans, home equity and second mortgage loans, and GNMA loans where trial period arrangement was unsuccessful	214
Government National Mortgage Association [Member] | Trouble Debt Restructure [Member]
Additional loans and allowance for credit losses (Textual) [Abstract]
Loans 90 days or more past due purchased from Government National Mortgage Association mortgage pools whose payments are insured by the Federal Housing Administration and classified with a pass rating	2,900,000,000		2,900,000,000			2,600,000,000
Restructured GNMA loans that are classified with a pass rating	2,100,000,000		2,100,000,000			2,000,000,000
Home equity and second mortgage loans [Member]
Additional loans and allowance for credit losses (Textual) [Abstract]
Number of loans in trial period	23		23
Outstanding balance of loans in trial period	3,000,000		3,000,000
Estimated post-modification balance of loans in trial period	$ 3,000,000		$ 3,000,000