Property, Plant and Equipment (Summary of Property by Classification) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment - Non-utility and other	$ 2,292	$ 1,960
Property, plant and equipment, Total	25,123	23,631
Less Accumulated Depreciation, Depletion and Amortization - Nonutility and Other	(767)	(676)
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(9,323)	(8,947)
Property, plant and equipment	15,800	14,684
Electric Generation Equipment [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment - Generation	11,127	10,383
Less Accumulated Depreciation, Depletion and Amortization - Generation	(4,004)	(3,880)
Electric Distribution [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment - Distribution	7,603	7,306
Less Accumulated Depreciation, Depletion and Amortization - Distribution	(2,947)	(2,837)
Electric Generation, Transmission and Distribution Equipment [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Plant in Service	18,730	17,689
Total Utility Accumulated Depreciation, Depletion and Amortization	(6,951)	(6,717)
Gas Distribution [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment - Distribution	2,834	2,704
Less Accumulated Depreciation, Depletion and Amortization - Distribution	(1,129)	(1,057)
Storage [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment - Storage	431	426
Less Accumulated Depreciation, Depletion and Amortization - Storage	(138)	(132)
Other [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment - Other	836	852
Less Accumulated Depreciation, Depletion and Amortization - Other	(338)	(365)
Gas Distribution and Storage [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Plant in Service	4,101	3,982
Total Utility Accumulated Depreciation, Depletion and Amortization	$ (1,605)	$ (1,554)