New And Significant Accounting Policies (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 for benefits earned	$ 99		$ 115
Interest cost	173		156
Expected return on plan assets	(202)		(162)
Amortization of prior service cost	5		5
Amortization of net actuarial loss	0		27
Net periodic benefit cost	75		141
Less: transfer to regulatory account	9	[1]	(57)	[1]
Total	84		84
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	11		13
Interest cost	19		19
Expected return on plan assets	(26)		(20)
Amortization of prior service cost	6		6
Amortization of net actuarial loss	0		1
Net periodic benefit cost	10		19
Less: transfer to regulatory account	0	[1]	0	[1]
Total	$ 10		$ 19

[1] The Utility recorded these amounts to a regulatory account since they are probable of recovery from customers in futures rates.