Guaranteed Benefit Features (Summary Of Guaranteed Death Benefit Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Guaranteed Benefit Features [Abstract]
Balance as of beginning-of-year	$ 89	$ 73	$ 104
Changes in reserves	52	34	(10)
Benefits paid	(26)	(18)	(21)
Balance as of end-of-period	$ 115	$ 89	$ 73