Investments (Schedule Of Changes in Amount Of Credit Losses Of OTTI Recognized In Net Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments [Abstract]
Balance as of beginning-of-period	$ 430	$ 382	$ 380
Increases attributable to:
Credit losses on securities for which an OTTI was not previously recognized	13	84	19
Credit losses on securities for which an OTTI was previously recognized	7	17	16
Decreases attributable to:
Securities sold, paid down or matured	(72)	(53)	(33)
Balance as of end-of-period	$ 378	$ 430	$ 382