Segment Information Information By Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 497,590	$ 446,746
Gross profit	163,203	138,422
Operating Income (Loss)	23,574	13,496
Total other income (expense)	(4,164)	(2,613)
Income Before Income Taxes	19,410	10,883
Electricity Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues	217,295	191,840
Gross profit	64,586	54,204
Operating Income (Loss)	10,632	1,114
Gas Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues	139,256	125,081
Gross profit	48,577	44,037
Operating Income (Loss)	16,299	14,491
Water Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues	141,039	129,825
Gross profit	50,040	40,181
Operating Income (Loss)	18,076	8,715
Corporate Unallocated [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (21,433)	$ (10,824)