Goodwill and Intangible Assets (Goodwill By Reportable Operating Segment) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	$ 16,072
Goodwill, Acquired During Period	3,353
Goodwill, balance at end of period	19,425
Electric Utilities and Infrastructure [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	15,656
Goodwill, Acquired During Period	1,723
Goodwill, balance at end of period	17,379
Gas Utilities and Infrastructure [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	294
Goodwill, Acquired During Period	1,630
Goodwill, balance at end of period	1,924
Commercial Renewables [Member]
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	122
Goodwill, balance at end of period	$ 122