Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 31	$ 26	$ 62	$ 52
Interest Cost	58	59	117	118
Expected Return on Plan Assets	(104)	(100)	(207)	(200)
Amortization of Prior Service Cost	(4)	(4)	(9)	(9)
Amortization of Actuarial Loss	37	14	74	28
Total Benefit Costs	18	(5)	37	(11)
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	6	4	11	9
Interest Cost	17	17	34	34
Expected Return on Plan Assets	(8)	(6)	(15)	(13)
Amortization of Prior Service Cost	(4)	(3)	(7)	(7)
Amortization of Actuarial Loss	11	6	21	12
Total Benefit Costs	$ 22	$ 18	$ 44	$ 35