Investments (Schedule Of Sources Of Net Investment Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investments, Debt and Equity Securities [Abstract]
Fixed maturities									$ 2,134	$ 2,196	$ 2,071
Short-term investments									28	43	34
Equity securities									34	36	26
Other									104	62	44
Gross investment income									2,300	2,337	2,175
Investment expenses									(119)	(95)	(105)
Net investment income	$ 567	$ 533	$ 537	$ 544	$ 565	$ 564	$ 569	$ 544	$ 2,181	$ 2,242	$ 2,070