Fair Value Measurements (Schedule Of Activity For Debt And Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Proceeds from sales and maturities of nuclear decommissioning trust investments	$ 282	$ 362	$ 721	$ 779
Gross realized gains on sales of securities held as available-for-sale	4	12	9	47
Gross realized losses on sales of securities held as available-for-sale	$ (1)	$ (10)	$ (3)	$ (13)