Securities (Details Textual) (USD $)	Mar. 31, 2012 MortgageObligation	Dec. 31, 2011	Mar. 31, 2011 Y
Securities (Textual) [Abstract]
Gross unrealized losses attributable to collateralized mortgage obligations	$ 1,000,000	$ 1,000,000	$ 40,000,000
Number of fixed rate collateralized mortgage obligations	33
Weighted-average maturity collateralized mortgage, in years			4.2
Pledged available for sale and Held-To-Maturity securities	$ 10,500,000,000

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor shall reclassify that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 15

-Subparagraph a

Name:	us-gaap_LoansPledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant