Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions		Jun. 30, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Number of Securities - Total | security		890	3,414
Fair Value Decline, Greater Than 20% [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months		$ 44	$ 395
Fair Value - Six months or greater, but less than nine months		47	96
Fair Value - Nine months or greater, but less than twelve months		2	11
Fair Value - Twelve months or greater		214	143
Fair Value - Total		307	645
Losses - Less than six months		15	124
Losses - Six months or greater, but less than nine months		16	49
Losses - Nine months or greater, but less than twelve months		1	8
Losses - Twelve months or greater		93	74
Gross Unrealized Losses - Total		125	255
OTTI - Less than six months		1	1
OTTI - Twelve months or greater		14	8
OTTI - Total		$ 15	$ 9
Number of Securities - Less than six months | security	[1]	15	45
Number of Securities - Six months or greater, but less than nine months | security	[1]	5	11
Number of Securities - Nine months or greater, but less than twelve months | security	[1]	2	2
Number of Securities - Twelve months or greater | security	[1]	35	32
Number of Securities - Total | security	[1]	57	90

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