Investments (Schedule Of Impaired Mortgage Loans) (Details) $ in Millions	Jun. 30, 2018 USD ($) item	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) item	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Information about impaired mortgage loans on real estate
Number of impaired mortgage loans on real estate | item	2		3
Principal balance of impaired mortgage loans on real estate	$ 8		$ 11
Valuation allowance associated with impaired mortgage loans on real estate	(2)	$ (3)	(3)	$ (2)	$ (2)	$ (2)
Carrying value of impaired mortgage loans on real estate	$ 6		$ 8