Derivative Instruments (Schedule Of Offsetting Assets And Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financial Assets
Derivative Instruments, Gross amount of recognized assets	$ 1,301	$ 1,470
Derivative Instruments, Gross amounts offset	(386)	(543)
Derivative Instruments, Net amount of assets	915	927
Derivative Instruments, Cash collateral	(765)	(894)
Derivative Instruments, Net amount	150	33
Embedded Derivative Instruments, Gross amount of recognized assets	965
Embedded Derivative Instruments, Gross amounts offset
Embedded Derivative Instruments, Net amount of assets	965
Embedded Derivative Instruments, Cash collateral
Embedded Derivative Instruments, Net amount	965
Total, Gross amount of recognized assets	2,266	1,470
Total, Gross amounts offset	(386)	(543)
Total, Net amount of assets	1,880	927
Total, Cash collateral	(765)	(894)
Total, Net amount	1,115	33
Financial Liabilities
Derivative Instruments, Gross amount of recognized liabilities	955	1,089
Derivative Instruments, Gross amounts offset	(296)	(536)
Derivative Instruments, Net amount of liabilities	659	553
Derivative Instruments, Cash collateral	(581)	(630)
Derivative Instruments, Net amount	78	(77)
Embedded Derivative Instruments, Gross amount of recognized liabilities	1,542	1,563
Embedded Derivative Instruments, Gross amounts offset
Embedded Derivative Instruments, Net amount of liabilities	1,542	1,563
Embedded Derivative Instruments, Cash collateral
Embedded Derivative Instruments, Net amount	1,542	1,563
Total, Gross amount of recognized liabilities	2,497	2,652
Total, Gross amounts offset	(296)	(536)
Total, Net amount of liabilities	2,201	2,116
Total, Cash collateral	(581)	(630)
Total, Net amount	$ 1,620	$ 1,486