Guaranteed Benefit Features (Summary Of Guaranteed Death Benefit Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Guaranteed Benefit Features [Abstract]
Balance as of beginning-of-year	$ 110	$ 115
Changes in reserves	(5)	15
Benefits paid	(6)	(14)
Balance as of end-of-period	$ 99	$ 116