Information By Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 477,592	$ 497,590
Gross profit	157,225	163,203
Operating Income (Loss)	30,042	23,574
Total other income (expense)	(4,981)	(4,164)
Income Before Income Taxes	25,061	19,410
Electricity Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues	238,751	217,295
Gross profit	67,192	64,586
Operating Income (Loss)	16,862	10,632
Gas Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues	124,211	139,256
Gross profit	50,504	48,577
Operating Income (Loss)	21,256	16,299
Water Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues	114,630	141,039
Gross profit	39,529	50,040
Operating Income (Loss)	8,735	18,076
Corporate Unallocated [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (16,811)	$ (21,433)