Fair Value Measurements (Schedule Of Activity For Debt And Equity Securities) (Details) - Entity [Domain] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Proceeds from sales and maturities of nuclear decommissioning trust investments	$ 362	$ 347	$ 779	$ 877
Gross realized gains on sales of securities held as available-for-sale	12	28	47	84
Gross realized losses on sales of securities held as available-for-sale	$ (10)	$ (2)	$ (13)	$ (3)