Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions		Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Nine months or greater, but less than twelve months		$ 5,673	$ 35,246
Fair Value - Twelve months or greater		1,848	8,671
Fair Value - Total		7,521	43,917
Losses - Nine months or greater, but less than twelve months		73	1,589
Losses - Twelve months or greater		170	856
Gross Unrealized Losses - Total		$ 243	$ 2,445
Number of Securities - Total | security		895	3,414
Fair Value Decline, Greater Than 20% [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months		$ 15	$ 395
Fair Value - Six months or greater, but less than nine months		10	96
Fair Value - Nine months or greater, but less than twelve months			11
Fair Value - Twelve months or greater		132	143
Fair Value - Total		157	645
Losses - Less than six months		5	124
Losses - Six months or greater, but less than nine months		3	49
Losses - Nine months or greater, but less than twelve months			8
Losses - Twelve months or greater		76	74
Gross Unrealized Losses - Total		$ 84	255
OTTI - Less than six months			1
OTTI - Twelve months or greater			8
OTTI - Total			$ 9
Number of Securities - Less than six months | security	[1]	7	45
Number of Securities - Six months or greater, but less than nine months | security	[1]	4	11
Number of Securities - Nine months or greater, but less than twelve months | security	[1]		2
Number of Securities - Twelve months or greater | security	[1]	31	32
Number of Securities - Total | security	[1]	42	90

[1] We may reflect a security in more than one aging category based on various purchase dates.