Investments (Activity related to the pretax fixed maturity credit loss component reflected within retained earnings for securities still held for which a portion of an OTTI loss was recognized in OCI) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance of credit losses on fixed maturity securities	$ 95	$ 92
Additional credit losses for securities for which an OTTI loss was previously recognized		11
Credit losses for securities for which an OTTI loss was not previously recognized		1
Reductions for securities sold during the period	(3)	(4)
Ending balance of credit losses on fixed maturity securities	$ 92	$ 100