Derivative Financial Instruments (Narrative) (Details) (USD $)	9 Months Ended	12 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Derivative liability, fair value	1,870,000,000
Collateral already posted, aggregate fair value	720,000,000
Maximum additional amount of payments related to termination events	1,150,000,000
Fair Value Hedges [Member]
Securities weighted-average life, years	7.4	7.7
Subordinated note matures	2018
Fair Value Hedges [Member] \| 4.956% Subordinated Note [Member]
Fixed interest rate	4.956%
Fair Value Hedges [Member] \| 5.25% Subordinated Note [Member]
Fixed interest rate	5.25%
Cash Flow Hedges [Member]
Securities weighted-average life, years	3.0	3.8

Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph a

-Clause 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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