Investments (Pretax Fixed Maturity Credit Loss Component Reflected Within Retained Earnings) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Investment Securities Held To Maturity [Line Items]
Beginning balance of credit losses on fixed maturity securities	$ 99	$ 82	$ 92	$ 141
Additional credit losses for securities for which an OTTI loss was previously recognized	2	11	23	29
Credit losses for securities for which an OTTI loss was not previously recognized		10	2	11
Reductions for securities sold during the period	(3)	(4)	(11)	(50)
Reductions for securities the Company intends to sell or more likely than not will be required to sell			(8)	(32)
Ending balance of credit losses on fixed maturity securities	$ 98	$ 99	$ 98	$ 99

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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