Guaranteed Benefit Features (Summary Of Guaranteed Death Benefit Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Guaranteed Benefit Features [Abstract]
Balance as of beginning-of-year	$ 161	$ 100
Changes in reserves	(36)	11
Benefits paid	(6)	(3)
Balance as of end-of-period	$ 119	$ 108