Investments (Activity related to the pretax fixed maturity credit loss component reflected within retained earnings for securities still held) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance of credit losses on fixed maturity securities	$ 192	$ 141	$ 164
Additional credit losses for securities for which an OTTI loss was previously recognized	93	39	37
Credit losses for securities for which an OTTI loss was not previously recognized	183	11	11
Reductions for securities sold during the period	(239)	(67)	(62)
Reductions for securities the Company intends to sell or more likely than not will be required to sell	(65)	(32)	(9)
Ending balance of credit losses on fixed maturity securities	$ 164	$ 92	$ 141

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

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This item represents reductions in the amount of cumulative losses recognized in earnings for other than temporary impairments (OTTI) for which a portion of the impairment had been recognized in other comprehensive income (a component of shareholders' equity) due to a change in status of the impaired security because of a change in the entity's intent to either sell the impaired security or it has become more likely than not that the entity will be required to sell the security before recovery of its cost basis.

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