Fair Value Measurements (Schedule Of Activity For Debt And Equity Securities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Proceeds from sales and maturities of nuclear decommissioning trust investments	$ 244	$ 182	$ 1,023	$ 1,059
Gross realized gains on sales of securities held as available-for-sale	3	30	50	114
Gross realized losses on sales of securities held as available-for-sale	$ (12)	$ 0	$ (25)	$ (3)