General (Details)	9 Months Ended
	Sep. 30, 2016 OperatingSegments OwnedAndOperatedCompanies
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | OperatingSegments	8
Number of owned and operated utility companies in the United States	4
Number of states owned and operated utility companies serve customers	11
Number of owned and operated interstate natural gas pipeline companies in the United States	2
Number of owned and operated electricity distribution companies in Great Britain	2
Number of owned and operated electricity transmission companies in Canada	1
Number of owned and operated renewable energy businesses	1
Number of owned and operated residential real estate brokerage firms in the United States	1
Number of owned and operated residential real estate brokerage franchise networks in the United States	1