Investments (Average Carrying Value On The Impaired Mortgage Loans On Real Estate) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Information about impaired mortgage loans on real estate
Average carrying value for impaired mortgage loans on real estate	$ 5	$ 8	$ 5	$ 6