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General (Details)
3 Months Ended
Mar. 31, 2014
OwnedAndOperatedCompanies
OperatingSegments
Other Ownership Interests [Line Items]  
Number of operating segments 10
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
Ownership interest in electric transmission businesses, ownership percentage 50.00%
Number of owned and operated eal estate brokerage firms in the United States 1
Number of owned and operated real estate franchise networks in the United States 1
Electric Transmission Texas, LLC [Member]
 
Other Ownership Interests [Line Items]  
Equity method investment, ownership percentage 50.00%
Electric Transmission America, LLC [Member]
 
Other Ownership Interests [Line Items]  
Equity method investment, ownership percentage 50.00%