Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) - Fair Value Decline, Greater Than 20% [Member] $ in Millions	Jun. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months	$ 274	$ 15
Fair Value - Six months or greater, but less than nine months	2	10
Fair Value - Twelve months or greater	27	132
Fair Value - Total	303	157
Gross Unrealized Losses - Less than six months	112	5
Gross Unrealized Losses - Six months or greater, but less than nine months	1	3
Gross Unrealized Losses - Twelve months or greater	16	76
Gross Unrealized Losses - Total	$ 129	$ 84
Number of Securities - Less than six months | security	51	7
Number of Securities - Six months or greater, but less than nine months | security	1	4
Number of Securities - Twelve months or greater | security	21	31
Number of Securities - Total | security	73	42