Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions	Mar. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Number of Securities - Total | security	2,670	882
Fair Value Decline, Greater Than 20% [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months		$ 15
Fair Value - Six months or greater, but less than nine months		10
Fair Value - Twelve months or greater		130
Fair Value - Total		155
Losses - Less than six months	$ 1,483	5
Losses - Six months or greater, but less than nine months		3
Losses - Twelve months or greater	50	74
Gross Unrealized Losses - Total	1,533	$ 82
OTTI - Less than six months	775
OTTI - Twelve months or greater	59
OTTI - Total	$ 834
Number of Securities - Less than six months | security	174	7
Number of Securities - Six months or greater, but less than nine months | security		4
Number of Securities - Twelve months or greater | security	23	31
Number of Securities - Total | security	197	42