Property, Plant and Equipment, Net (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Utility plant in-service:
Common general	$ 219	$ 212
Utility plant in-service	3,786	3,764
Accumulated depreciation and amortization	(1,316)	(1,301)
Utility plant in-service, net	2,470	2,463
Construction work-in-progress	96	89
Property, plant and equipment, net	2,566	2,552
Electric Plant [Member]
Utility plant in-service:
Generation	1,071	1,070
Distribution	1,297	1,289
Transmission	685	685
Intangible plant	143	138
Gas Plant [Member]
Utility plant in-service:
Distribution	358	357
Intangible plant	$ 13	$ 13