Derivative Financial Instruments (Effect Of Non-Hedging Derivatives On Income Statement And Included In Net Realized Gains (Losses) On Financial Instruments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) Recognized	$ 2	$ (13)	$ 22	$ (37)
Interest Rate Swaps [Member] | Net realized gains (losses) on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) Recognized	0	0	15	(1)
Options [Member] | Net realized gains (losses) on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) Recognized	0	(13)	0	(34)
Futures [Member] | Net realized gains (losses) on financial instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) Recognized	$ 2	$ 0	$ 7	$ (2)