Contingent Liabilities and Guarantees (Details Textual) (USD $) In Billions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012 Y
Standby letters of credit
Remaining Weighted Average Life of Standby Letters of Credit	3.0
Remaining actual life	From less than one year to as many as eleven years
Recourse agreement with FNMA
Weighted average remaining term for outstanding commercial mortgage loans	6
Unpaid principal balance outstanding of loans sold	$ 3.0
Potential undiscounted future payments, maximum limit	One-third of principal balance of loan outstanding
Written put options
Weighted average life of written put options	1.8
Default guarantees
Terms of default guarantees range	From less than 1 year to as many as 7 years