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Segment Information Major Customers (Details)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Revenue, Major Customer [Line Items]    
Segment Reporting, Disclosure of Major Customers For the three months ended March 31, 2017, no single customer represented more than 10% of total Company, or the Gas, or Water operating segment revenues. For the three months ended March 31, 2016, no single customer represented more than 10% of total Company, or the Gas, or Water operating segment revenues.
Revenue [Member] | Threshold for Reporting Customer Concentration [Member]    
Revenue, Major Customer [Line Items]    
Concentration Risk, Percentage 10.00% 10.00%
Revenue [Member] | Customer A [Member] | Electricity Operating Segment [Member]    
Revenue, Major Customer [Line Items]    
Concentration Risk, Percentage 18.00% 13.00%