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	12 Months Ended
	Dec. 31, 2012	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	$ 92	$ 141	$ 164
Additional credit losses for securities for which an OTTI loss was previously recognized	23	39	37
Credit losses for securities for which an OTTI loss was previously recognized	2	11	11
Reductions for securities sold during the period	(14)	(67)	(62)
Reductions for securities the Company intends to sell or more likely than not will be required to sell	(8)	(32)	(9)
Ending balance of credit losses on fixed maturity securities	$ 95	$ 92	$ 141