Investments (Changes In The Valuation Allowance Of Impaired Mortgage Loans On Real Estate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Losses
Balance as of beginning-of-period	$ 2	$ 2	$ 3
Additions	1	1
Charge-offs, net of recoveries		(1)	(1)
Balance as of end-of-period	$ 3	$ 2	$ 2