Segment Information Depreciation and Amortization, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 16,674	$ 19,355
Electricity Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	7,262	9,149
Gas Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	4,921	5,341
Water Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	4,382	4,792
Corporate Unallocated [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 109	$ 73