Derivative Financial Instruments (Details 4) (Net investment income, USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2012
Interest rate contracts
Derivative Instruments Change in Fair Value of Fair Value Hedges
Gain (loss) on derivatives	$ 1	$ 3
Investments
Derivative Instruments Change in Fair Value of Fair Value Hedges
Gain (loss) on hedged risk	$ (1)	$ (3)

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration