Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) - Fair Value Decline, Greater Than 20% [Member] $ in Millions	Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months	$ 12	$ 63
Fair Value - Six months or greater, but less than nine months		2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		23
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	58	30
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	70	118
Gross Unrealized Losses - Less than six months	3	23
Gross Unrealized Losses - Six months or greater, but less than nine months		1
Less Than or Equal to Twelve Months		7
Greater Than Twelve Months	8	11
Fair Value - Total	$ 11	$ 42
Number of Securities - Less than six months | security	6	14
Number of Securities - Six months or greater, but less than nine months | security		4
Number of Securities - Nine months or greater, but less than twelve months | security		14
Number of Securities - Twelve months or greater | security	24	20
Number of Securities - Total | security	30	52