Fair Value of Assets and Liabilities (Details Textual) (USD $) In Billions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Loans Security	Mar. 31, 2012 Security
Fair Value (Additional Textual) [Abstract]
Number of debt securities with other-than-temporary impairment	2	18
Minimum effective discount rate on overall basis	5.34%
Maximum effective discount rate on overall basis	19.72%
Minimum assets of trust preferred securities issued by institution	$ 15.0
Maturity period of short-term borrowings	one year or less
Period of swap rate	25 years
Beginning year for projected prepayments for all banks	2018
Healthy banks projected default percentage for remaining period	0.36%
Historical default rates initial calculation period	2 years
Floating spread rate of trust preferred securities	0.0300
Number of impaired loans discounted	1
Trust preferred securities
Fair Value (Textual) [Abstract]
Projected Prepayments, minimum fixed rate coupons	8.00%
Projected Prepayments, minimum floating rate spreads	3.00%
Projected Prepayments, percentage of fair value input for banks	1.00%
Period frequency of projected prepayment rate	5 years
Projected prepayment, percentage of fair value for collateral by REITs or insurance companies	0.00%
Annually projected defaults percentage for healthy banks	2.00%
Projected recovery, percentage for projected bank deferrals	10.00%
Projected defaults rate for healthy banks	0.00%
Trust preferred securities | Minimum
Fair Value (Textual) [Abstract]
Fair value input discount rate	5.34%
Trust preferred securities | Maximum
Fair Value (Textual) [Abstract]
Fair value input discount rate	19.72%