Investments and Derivative Instruments (Details Textual 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Other liabilities, variable interest entity liabilities	$ 461	$ 471
Non-Consolidated VIEs [Member]
Variable Interest Entity [Line Items]
Assets	27	28
Other liabilities, variable interest entity liabilities	25	28
Company's maximum exposure to the loss of the contingent capital facility	$ 3	$ 3

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=6970148&loc=d3e5710-111685

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- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=6970148&loc=d3e5728-111685

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS140-4/FIN46(R)

-Paragraph C6

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (c)

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