Pension, OPEB and Savings Plans (Components Of Net Periodic Benefit Cost) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 116	$ 101	$ 92
Interest Cost	215	223	228
Expected Return on Plan Assets	(348)	(306)	(334)
Amortization of Net Transition Obligation	0	0	0
Amortization of Prior Service Cost	(19)	(18)	(11)
Amortization of Actuarial Loss	188	167	119
Net Periodic Benefit Cost	152	167	94
Special Termination Benefits	0	1
Effect of Regulatory Asset	0	0
Total Benefit Costs, Including Effect of Regulatory Asset	152	168	94
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	21	17	14
Interest Cost	63	65	61
Expected Return on Plan Assets	(21)	(17)	(18)
Amortization of Net Transition Obligation	0	2	4
Amortization of Prior Service Cost	(14)	(14)	(13)
Amortization of Actuarial Loss	42	31	14
Net Periodic Benefit Cost	91	84	62
Effect of Regulatory Asset	0	19	19
Total Benefit Costs, Including Effect of Regulatory Asset	$ 91	$ 103	$ 81