Summary of Significant Accounting Policies Property, Plant and Equipment, Net (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Buildings, machinery and equipment	$ 15,154	$ 15,074
Geothermal properties	1,199	1,163
Other	157	156
Property, Plant and Equipment, Gross	16,510	16,393
Less: Accumulated depreciation	4,405	4,158
Property, Plant and Equipment, Gross, Less Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	12,105	12,235
Land	90	91
Construction in progress	914	693
Property, plant and equipment, net	$ 13,109	$ 13,019