Financial Derivatives (Risk Participation Agreements Sold) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Notional Amount of Credit Risk Derivatives	$ 493	$ 761
Risk Participation Agreements Sold [Member]
Notional Amount of Credit Risk Derivatives	1,668	1,367
Estimated Net Fair Value	$ (5)	$ (2)
Weighted-Average Remaining Maturity In Years of Risk Participation Agreements Sold	7.3	2.0

Aggregate notional amount of credit risk derivatives.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5580258-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5579245-113959

Name:	us-gaap_NotionalAmountOfCreditRiskDerivatives
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant