Investments and Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Investments and Derivative Instruments [Abstract]
Document Period End Date	Mar. 31, 2013
Change in non-credit impairments of debt securities recognized in OCI
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 15	$ (8)

Net of tax amount of other than temporary impairment (OTTI) on a debt security, categorized as available-for-sale or held-to-maturity, recognized in other comprehensive income (loss), attributable to the parent entity.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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