CONDENSED CONSOLIDATED STATEMENTS OF INCOME Unaudited - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Operating revenue	$ 171,132	$ 152,445	$ 293,168	$ 274,172
Operations:
Water production costs	64,131	57,589	106,199	98,658
Administrative and general	23,796	23,366	49,045	51,193
Other operations	18,328	18,903	34,452	38,205
Maintenance	4,708	5,934	10,820	11,997
Depreciation and amortization	19,218	15,842	38,419	31,888
Income taxes	9,635	6,870	8,751	5,945
Property and other taxes	6,057	5,407	12,173	11,482
Total operating (income) expense	145,873	133,911	259,859	249,368
Net operating income (loss)	25,259	18,534	33,309	24,804
Other income and expenses:
Non-regulated revenue	3,739	3,764	7,201	7,192
Non-regulated expenses	(1,614)	(2,809)	(3,668)	(5,789)
Allowance for equity funds used during construction	879	0	1,658	0
Income tax expense on other income and expenses	(1,217)	(384)	(2,106)	(565)
Net other income	1,787	571	3,085	838
Interest expense:
Interest expense	9,079	8,434	17,789	16,499
Allowance for borrowed funds used during construction	(564)	(837)	(1,058)	(1,567)
Net interest expense	8,515	7,597	16,731	14,932
Net income	$ 18,531	$ 11,508	$ 19,663	$ 10,710
Earnings per share:
Basic (in dollars per share)	$ 0.39	$ 0.24	$ 0.41	$ 0.22
Diluted (in dollars per share)	$ 0.39	$ 0.24	$ 0.41	$ 0.22
Weighted average shares outstanding:
Basic (in shares)	48,020	47,972	48,002	47,938
Diluted (in shares)	48,020	47,972	48,002	47,943
Dividends declared per share of common stock (in dollars per share)	$ 0.18	$ 0.1725	$ 0.3600	$ 0.3450