Segment Information Depreciation and Amortization, by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 19,754	$ 24,627	$ 58,514	$ 75,233
Electricity Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	8,875	11,596	27,419	36,754
Gas Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	5,502	6,486	16,045	19,590
Water Operating Segment [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	5,282	6,466	14,810	18,679
Corporate Unallocated [Member]
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 95	$ 79	$ 240	$ 210