Investments (Net Realized Investment Gains/Losses And Net Change In Unrealized Appreciation/Depreciation On Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Net realized gains (losses) on investments	$ 184	$ 84	$ (229)
Total change in net unrealized gains (losses) on investments	570	874	(524)
Deferred income tax (expense) benefit	(142)	(194)	106
Change in net unrealized gains (losses) on investments	428	680	(418)
Net realized gains (losses) on investments and change in net unrealized gains (losses) on investments	612	764	(647)
Fixed Maturity Securities [Member]
Investment [Line Items]
Gross realized gains from sales	175	125	85
Gross realized losses from sales	(105)	(59)	(116)
Impairment losses recognized in income	(7)	(13)	(9)
Net realized gains (losses) from sales	63	53	(40)
Total change in net unrealized gains (losses) on investments	575	874	(529)
Equity Securities [Member]
Investment [Line Items]
Gross realized gains from sales	269	147	77
Gross realized losses from sales	(75)	(84)	(276)
Net realized gains (losses) from sales	194	63	(199)
Total change in net unrealized gains (losses) on investments	0	0	0
Other Investments [Member]
Investment [Line Items]
Impairment losses recognized in income	(91)	(34)	(17)
Gross realized gains from sales	18	3	27
Gross realized losses from sales	0	(1)	0
Net realized gains (losses) from sales of other investments	(73)	(32)	10
Total change in net unrealized gains (losses) on investments	$ (5)	$ 0	$ 5