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		$ 5,482	$ 33,630
Fair Value - Twelve months or greater		1,820	8,386
Fair Value - Total		7,302	42,016
Losses - Nine months or greater, but less than twelve months		70	1,521
Losses - Twelve months or greater		159	818
Gross Unrealized Losses - Total		$ 229	$ 2,339
Number of Securities - Total | security		882	3,360
Fair Value Decline, Greater Than 20% [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months		$ 15	$ 389
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		130	138
Fair Value - Total		155	634
Losses - Less than six months		5	122
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		74	70
Gross Unrealized Losses - Total		$ 82	249
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	44
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	89

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