Investments (Net Realized Investment Gains/Losses And Net Change In Unrealized Appreciation/Depreciation On Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Net realized gains (losses) on investments	$ 131	$ (203)	$ 200
Other-than-temporary impairment losses recognized in income	(47)	(26)	(33)
Total change in net unrealized gains (losses) on investments	874	(524)	257
Deferred income tax (expense) benefit	(194)	106	(84)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	680	(418)	173
Net realized gains (losses) on investments, other-than-temporary impairment losses recognized in income and net change in net unrealized gains (losses) on investments	764	(647)	340
Fixed Maturity Securities [Member]
Investment [Line Items]
Gross realized gains from sales	125	85	137
Gross realized losses from sales	(59)	(116)	(55)
Net realized gains (losses) from sales	66	(31)	82
Other-than-temporary impairment losses recognized in income	(13)	(9)	(4)
Total change in net unrealized gains (losses) on investments	874	(529)	156
Equity Securities [Member]
Investment [Line Items]
Gross realized gains from sales	147	77	140
Gross realized losses from sales	(84)	(276)	(17)
Net realized gains (losses) from sales	63	(199)	123
Other-than-temporary impairment losses recognized in income	0	0	(15)
Total change in net unrealized gains (losses) on investments	0	0	111
Other Investments [Member]
Investment [Line Items]
Gross realized gains from sales	3	27	0
Gross realized losses from sales	(1)	0	(5)
Net realized gains (losses) from sales of other investments	2	27	(5)
Other-than-temporary impairment losses recognized in income	(34)	(17)	(14)
Total change in net unrealized gains (losses) on investments	$ 0	$ 5	$ (10)