Derivative Instruments (Gains (Losses) On Derivative Instruments Designated As Cash Flow Hedges) (Details) - Designated as Hedging Instrument [Member] - Cash flow hedges - Other Comprehensive Income (Loss) [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gains (losses) on derivative instruments designated and qualifying as cash flow hedges
Offset to net investment income	$ 4	$ 4	$ 7	$ 7
Offset to realized gain (loss)			4
Offset to interest and debt expense	$ (2)	$ 1	$ (2)	$ 1