Property, Plant and Equipment, Net (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Utility plant in-service:
Common general	$ 233	$ 212
Utility plant in-service	3,819	3,764
Accumulated depreciation and amortization	(1,324)	(1,301)
Utility plant in-service, net	2,495	2,463
Construction work-in-progress	87	89
Property, plant and equipment, net	2,582	2,552
Electric Plant [Member]
Utility plant in-service:
Generation	1,067	1,070
Distribution	1,308	1,289
Transmission	714	685
Intangible plant	124	138
Gas Plant [Member]
Utility plant in-service:
Distribution	360	357
Intangible plant	$ 13	$ 13