Investments (Schedule Of Sources Of Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Investment Income [Line Items]
Gross investment income									$ 3,006	$ 2,308	$ 2,371
Investment expenses									(141)	(114)	(119)
Net investment income	$ 744	$ 739	$ 708	$ 674	$ 532	$ 549	$ 562	$ 551	2,865	2,194	2,252
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross investment income									2,779	2,157	2,199
Short-term investments
Net Investment Income [Line Items]
Gross investment income									93	49	45
Equity securities
Net Investment Income [Line Items]
Gross investment income									36	16	33
Other Investments [Member]
Net Investment Income [Line Items]
Gross investment income									$ 98	$ 86	$ 94