Property, Plant and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Net property, plant and equipment	$ 102,127	$ 91,694
Impairment charges	(8)	$ 402	$ 282
Wind project
Property, Plant and Equipment [Line Items]
Impairment charges			69
Renewable merchant plants
Property, Plant and Equipment [Line Items]
Net property, plant and equipment	$ 160
Property, plant and equipment
Property, Plant and Equipment [Line Items]
Impairment charges			58
Net intangible assets
Property, Plant and Equipment [Line Items]
Impairment charges			$ 11