Pension And Other Postretirement Employee Benefits (OPEB) Plans (Recognized Net Periodic Pension And Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Net costs	$ 39	$ 25	$ 78	$ 51
Less amounts deferred principally as property or a regulatory asset	(28)	(16)	(56)	(33)
Net amounts recognized as expense	11	9	22	18
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	6	12	12
Interest cost	33	33	66	66
Expected return on assets	(29)	(34)	(58)	(68)
Amortization of net loss	16	10	32	20
Net costs	26	15	52	30
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	4	3
Interest cost	11	11	22	22
Expected return on assets	(3)	(3)	(6)	(6)
Amortization of prior service cost	(5)	(5)	(10)	(10)
Amortization of net loss	8	6	16	12
Net costs	$ 13	$ 10	$ 26	$ 21