Property, Plant and Equipment (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Electric Utility [Abstract]
Property Plant and Equipment Accumulated Depreciation Nonutility and Other	$ (688)	$ (525)
Gas Utility [Abstract]
Storage	406	395
Other	902	991
Storage	(127)	(108)
Other	(413)	(512)
Non-utility and other	1,884	1,660
Total	22,541	21,574
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	8,795	8,582
Net Property, Plant and Equipment	13,746	12,992
Electric Generation, Transmission and Distribution Equipment [Member]
Electric Utility [Abstract]
Generation	9,785	9,268
Distribution	7,003	6,800
Generation	(3,946)	(3,850)
Distribution	(2,580)	(2,568)
Total Electric Utility	(6,526)	(6,418)
Public Utilities, Property, Plant and Equipment, Plant in Service	16,788	16,068
Gas, Transmission and Distribution Equipment [Member]
Electric Utility [Abstract]
Distribution	2,561	2,460
Distribution	(1,041)	(1,019)
Total Electric Utility	(1,581)	(1,639)
Public Utilities, Property, Plant and Equipment, Plant in Service	$ 3,869	$ 3,846