Pension And OPEB (Components Of Net Periodic Benefit Cost) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 26	$ 29
Interest Cost	59	54
Expected Return on Plan Assets	(100)	(87)
Amortization of Prior Service Cost	(5)	(5)
Amortization of Actuarial Loss	14	47
Total Benefit Costs	(6)	38
OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	5	5
Interest Cost	17	16
Expected Return on Plan Assets	(7)	(5)
Amortization of Prior Service Cost	(4)	(4)
Amortization of Actuarial Loss	6	11
Total Benefit Costs	$ 17	$ 23