Membership Interests (Schedule Of Changes To Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (107)
Balance at end of period	(105)
Cash Flow Hedges - Interest Rate Swap [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (24)	$ (26)
Defined benefit pension plans (net of tax)
Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges	$ 1	1
Balance at end of period	(23)	(25)
Defined Benefit Pension and OPEB Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(83)	(22)
Defined benefit pension plans (net of tax)	$ 1
Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges
Balance at end of period	$ (82)	(22)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(107)	(48)
Defined benefit pension plans (net of tax)	1
Amounts reclassified from accumulated other comprehensive income (loss) and reported in interest expense and related charges	1	1
Balance at end of period	$ (105)	$ (47)