Segment Information Depreciation and Amortization, by Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 19,339	$ 25,592
Electricity Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	9,147	12,767
Gas Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	5,326	6,649
Water Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	4,793	6,094
Corporate Unallocated [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 73	$ 82