Investments (Schedule Of Net Investment Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	$ 2,121		$ 2,562		$ 2,549
Investment expenses	(58)		(54)		(50)
Net investment income	2,063		2,508		2,499
Investment gains (losses)	(52)	[1]	56	[1]	(853)	[1]
Net unrealized gains on trading securities	(58)		88		94
Gross realized gains on available-for-sale securities	299		525		973
Gross realized losses on available-for-sale securities	322		435		1,897
Net change in unrealized gains (losses) in available-for-sale investments	1,437		1,146		5,430
Fixed Maturity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	2,011		2,052		1,941
Investment gains (losses)	(22)		92		(1,167)
Net change in unrealized gains (losses) in available-for-sale investments	1,442		1,140		5,278
Short Term Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	16		22		42
Investment gains (losses)			7		14
Limited Partnerships [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	97		315		324
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	20		32		49
Investment gains (losses)	(1)		(2)		243
Net change in unrealized gains (losses) in available-for-sale investments	(2)		7		156
Income (Loss) From Trading Portfolio [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	(39)	[2]	131	[2]	187	[2]
Other Investment Income [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total investment income	16		10		6
Investment gains (losses)	5		(10)		6
Net change in unrealized gains (losses) in available-for-sale investments	(3)		(1)		(4)
Derivative Instruments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment gains (losses)	$ (34)		$ (31)		$ 51

[1] Includes gross realized gains of $299, $525 and $973 and gross realized losses of $322, $435 and $1,897 on available-for-sale securities for the years ended December 31, 2011, 2010 and 2009.

[2] Includes net unrealized gains (losses) related to changes in fair value on trading securities still held of $(58), $88 and $94 for the years ended December 31, 2011, 2010 and 2009