Dividends (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	1 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2012	Feb. 25, 2011	Jan. 24, 2011	Dec. 17, 2010	Oct. 20, 2010	Sep. 24, 2010	Aug. 18, 2010	Jun. 11, 2010	Apr. 14, 2010	Mar. 12, 2010	Dec. 16, 2009	Sep. 30, 2012	Jun. 30, 2012	Jan. 31, 2012	Sep. 30, 2011	Jul. 31, 2011	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2011	Dec. 31, 2012
Dividends
Dividend Per Share (in dollars per share)			$ 0.08		$ 0.08		$ 0.08		$ 0.08		$ 0.08
Total amount declared			$ 141		$ 139		$ 139		$ 139		$ 138		$ 550	$ 38	$ 500	$ 42	$ 28
Dividends paid	$ 550	$ 141		$ 139		$ 139		$ 139		$ 138		$ 200		$ 38	$ 300		$ 28	$ 42	$ 300	$ 750

Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 20

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 18

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585

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