New And Significant Accounting Policies (Components Of Net Periodic Benefit Cost) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	$ 96		$ 115		$ 195		$ 230
Interest cost	173		156		346		312
Expected return on plan assets	(201)		(163)		(403)		(325)
Amortization of prior service cost	5		5		10		10
Amortization of net actuarial loss	1		28		1		55
Net periodic benefit cost	74		141		149		282
Less: transfer to regulatory account	9	[1]	(56)	[1]	19		(113)
Total	83		85		168		169
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	11		13		22		26
Interest cost	19		18		38		37
Expected return on plan assets	(26)		(20)		(52)		(40)
Amortization of prior service cost	5		5		11		11
Amortization of net actuarial loss	1		2		1		3
Net periodic benefit cost	10		18		20		37
Less: transfer to regulatory account	0	[1]	0	[1]	0	[1]	0	[1]
Total	$ 10		$ 18		$ 20		$ 37

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