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Basis of Presentation and Summary of Significant Accounting Policies Property, Plant and Equipment, Net (Details) - USD ($)
$ in Millions
Jun. 30, 2015
Dec. 31, 2014
Property, Plant and Equipment [Line Items]    
Buildings, machinery and equipment $ 16,422 $ 16,059
Geothermal properties 1,320 1,294
Other 208 203
Property, Plant and Equipment, Gross 17,950 17,556
Less: Accumulated depreciation 5,236 4,984
Property, Plant and Equipment, Gross, Less Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment 12,714 12,572
Land 121 120
Construction in progress 312 498
Property, plant and equipment, net $ 13,147 $ 13,190