Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions	Sep. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Number of Securities - Total | security	1,191	882
Fair Value Decline, Greater Than 20% [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months	$ 171	$ 15
Fair Value - Six months or greater, but less than nine months	126	10
Fair Value - Twelve months or greater	30	130
Fair Value - Total	327	155
Gross Unrealized Losses - Less than six months	62	5
Gross Unrealized Losses - Six months or greater, but less than nine months	54	3
Gross Unrealized Losses - Twelve months or greater	13	74
Gross Unrealized Losses - Total	$ 129	82
OTTI - Less than six months
OTTI - Six months or greater, but less than nine months
OTTI - Twelve months or greater
OTTI - Total
Number of Securities - Less than six months | security	27	7
Number of Securities - Six months or greater, but less than nine months | security	21	4
Number of Securities - Twelve months or greater | security	22	31
Number of Securities - Total | security	70	42