Organization, Basis of Presentation and Significant Accounting Policies (Details 3) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment
In service	$ 43,210	$ 40,122
Less - Accumulated provision for depreciation	(12,600)	(11,839)
Property, plant and equipment in service net of accumulated provision for depreciation	30,610	28,283
Unregulated
Property, Plant and Equipment
In service	16,658	15,472
Less - Accumulated provision for depreciation	(4,870)	(4,424)
Property, plant and equipment in service net of accumulated provision for depreciation	11,788	11,048
Regulated
Property, Plant and Equipment
In service	26,552	24,650
Less - Accumulated provision for depreciation	(7,730)	(7,415)
Property, plant and equipment in service net of accumulated provision for depreciation	$ 18,822	$ 17,235