COMMITMENTS AND CONTINGENCIES (Detail 2) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($)	Dec. 31, 2017 acrefoot	Dec. 31, 2016 USD ($) entity $ / acrefoot acrefoot	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jul. 21, 2016 gal
Long-term purchase commitments - other disclosures
Contingency loss recognized liability			$ 6,000
Water Control Board and Fish and Wildlife Complaint [Member]
Long-term purchase commitments - other disclosures
Loss contingency, alleged number of gallons discharged | gal						8,207,560
Santa Clara Valley Water District
Long-term purchase commitments - other disclosures
Annual cost			8,500	$ 6,300	$ 5,500
Stockton East Water District (SEWD)
Long-term purchase commitments - other disclosures
Annual cost			$ 12,200	$ 9,800	$ 8,700
Kern County Water Agency (Agency)
Long-term purchase commitments - other disclosures
Minimum acre feet of treated water to be purchased per year over life of contract | acrefoot			20,000
Minimum acre feet of treated water to be purchased under prior agreement | $ / acrefoot			11,500
Number of other parties obligated to purchase treated water | entity			3
Minimum acre feet of treated water to be purchased per year by other parties | acrefoot			32,500
Total obligation of all parties, excluding the Company			$ 82,400
Total capital facilities charge and treated water charge obligation			$ 9,100
Total capital facilities charge and treated water charge obligation per acre foot | $ / acrefoot			443.1
Total treated water charge			$ 3,200
Portion of estimated operating cost per acre foot for treated water delivered | $ / acrefoot			63.9
Kern County Water Agency (Agency) | Scenario, Forecast [Member]
Long-term purchase commitments - other disclosures
Minimum acre feet of treated water to be purchased per year over life of contract | acrefoot		20,500
Water Control Board [Member] | Water Control Board and Fish and Wildlife Complaint [Member]
Long-term purchase commitments - other disclosures
Payments for legal settlements	$ 500
Fish and Wildlife [Member] | Water Control Board and Fish and Wildlife Complaint [Member]
Long-term purchase commitments - other disclosures
Payments for legal settlements	$ 20