Contingent Liabilities and Guarantees (Details Texual) (USD $)	3 Months Ended
	Mar. 31, 2012 Y
Standby letters of credit
Remaining Weighted Average Life of Standby Letters of Credit	2.9
Remaining actual life	From less than one year to as many as ten years
Recourse agreement with FNMA
Weighted average remaining term for outstanding commercial mortgage loans	6
Unpaid principal balance outstanding of loans sold	$ 2,900,000,000
Potential undiscounted future payments, maximum limit	One-third of principal balance of loan outstanding
Written put options
Weighted average life of written put options	1.7
Default guarantees
Terms of default guarantees range	From less than 1 year to as many as 7 years
Other Off-Balance Sheet Risk
Obligation for credit market disruption	51,000,000
Expiration date of liquidity facility	May 31, 2012
Aggregate amount available to be drawn of current commitments	$ 30,000,000