Guaranteed Benefit Features (Summary Of Guaranteed Death Benefit Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Guaranteed Benefit Features [Abstract]
Balance as of beginning-of-year	$ 115	$ 89	$ 73
Changes in reserves	34	52	34
Benefits paid	(39)	(26)	(18)
Balance as of end-of-period	$ 110	$ 115	$ 89