Investments (Composition Of Current And Past Due Mortgage Loans On Real Estate) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Mortgage Loans On Real Estate Aging [Abstract]
Current	$ 10,000	$ 9,888
Greater than 90 days past due	2	2
Valuation allowance associated with impaired mortgage loans on real estate	(2)	(2)	$ (2)	$ (2)
Unamortized premium (discount)	1	1
Total carrying value	$ 10,001	$ 9,889