Commitments and Contingencies (Narrative) (Details) (USD $)	9 Months Ended
Sep. 30, 2011 days	Dec. 31, 2010	Sep. 30, 2010
Commitments to Extend Credit [Member]
Guarantor Obligations [Line Items]
Unused commitments	$ 5,890,000,000	$ 5,360,000,000	$ 5,230,000,000
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor obligations amount	57,900,000	70,800,000	77,900,000
Recourse Obligation on Mortgage Loans Sold [Member]
Guarantor Obligations [Line Items]
Recourse period, maximum, in days	120
Guarantor obligations amount	$ 217,000,000	$ 253,300,000	$ 256,700,000

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 13

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant