Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
OPERATING REVENUE	$ 86,944	$ 72,402	$ 148,056	$ 134,514
Production Expenses:
Purchased water	14,485	16,002	24,182	25,286
Power	1,614	1,528	2,851	2,700
Groundwater extraction charges	8,312	6,197	14,760	14,133
Other production expenses	3,272	3,065	6,504	6,062
Total production expenses	27,683	26,792	48,297	48,181
Administrative and general	11,536	11,464	23,241	22,760
Maintenance	4,054	3,844	7,865	7,212
Property taxes and other non-income taxes	2,684	2,890	5,902	5,985
Depreciation and amortization	11,187	10,202	22,370	20,361
Total operating expense	57,144	55,192	107,675	104,499
OPERATING INCOME	29,800	17,210	40,381	30,015
OTHER (EXPENSE) INCOME:
Interest on long-term debt	(5,007)	(5,299)	(10,046)	(10,638)
Mortgage and other interest expense	(462)	(319)	(858)	(632)
Gain on sale of California Water Service Group stock	3,197	0	3,197	0
Dividend income	8	44	53	87
Other, net	150	230	459	523
Income before income taxes	27,686	11,866	33,186	19,355
Provision for income taxes	10,911	4,405	13,033	7,199
NET INCOME	16,775	7,461	20,153	12,156
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on investment	487	(255)	1,017	(270)
Reclassification adjustment for gain realized on sale of investments	(1,742)	0	(1,742)	0
COMPREHENSIVE INCOME	$ 15,520	$ 7,206	$ 19,428	$ 11,886
EARNINGS PER SHARE
Basic (usd per share)	$ 0.82	$ 0.37	$ 0.99	$ 0.60
Diluted (usd per share)	0.82	0.36	0.98	0.59
DIVIDENDS PER SHARE (usd per share)	$ 0.20	$ 0.20	$ 0.41	$ 0.39
WEIGHTED AVERAGE SHARES OUTSTANDING
Basic (shares)	20,437,612	20,357,068	20,425,678	20,342,064
Diluted (shares)	20,578,585	20,501,437	20,569,790	20,490,938