Investments (Composition Of Current And Past Due Mortgage Loans On Real Estate) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Mortgage Loans On Real Estate Aging [Abstract]
Current	$ 10,023		$ 9,888
Greater than 90 days past due	2		2
Valuation allowance associated with impaired mortgage loans on real estate	(2)	$ (2)	(2)	$ (2)	$ (2)	$ (2)
Unamortized premium (discount)			1
Total carrying value	$ 10,023		$ 9,889