Basis of Presentation and Summary of Significant Accounting Policies Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Buildings, machinery and equipment	$ 16,512	$ 16,506
Geothermal properties	1,500	1,494
Other	252	236
Property, plant and equipment, gross	18,264	18,236
Less: Accumulated depreciation	6,545	6,383
Property, plant and equipment, gross, less accumulated depreciation, depletion and amortization	11,719	11,853
Land	117	117
Construction in progress	787	754
Property, plant and equipment, net	$ 12,623	$ 12,724
Minimum [Member] | Rotable Parts [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	1 year 6 months
Minimum [Member] | Building, Machinery and Equipment, Gross [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	3 years
Minimum [Member] | Geothermal Properties, Gross [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	13 years
Minimum [Member] | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	3 years
Maximum [Member] | Rotable Parts [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	12 years
Maximum [Member] | Building, Machinery and Equipment, Gross [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	46 years
Maximum [Member] | Geothermal Properties, Gross [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	58 years
Maximum [Member] | Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, estimated useful lives	46 years