Investments (Changes in Fixed Maturity Securities with Noncredit OTTI Losses) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Changes in fixed maturity securities with noncredit OTTI losses in accumulated other comprehensive income (loss)
Balance, beginning of period	$ (64)	$ (125)
Noncredit OTTI losses recognized	11	(3)
Securities sold with a previous noncredit OTTI loss	18	35
Subsequent increases in estimated fair value	(9)	29
Balance, end of period	(44)	(64)
Non Credit Otti Losses On Debt Securities Recognized Net Of Dac Included In Accumulated Other Comprehensive Income (Loss)	$ 9	$ 5