REVENUE RECOGNITION, Disaggregated Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
REVENUE RECOGNITION [Abstract]
Refund to customers through reduced tariff rates				$ (3,800)
Minimum number of days for accounts receivable from tariff contract customers			25 days
Increase in reserve for bad debt	$ 300		$ 300
Minimum number of days due for accounts receivable from SLP Plan customer			25 days
Minimum number of days customers services invoiced in advance			30 days
Disaggregation of Revenue [Abstract]
Other Operating Revenue not in scope of ASC 606	324	$ 311	$ 616	612
Total Operating Revenues	21,752	20,652	41,653	40,037
Tariff Revenue [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	20,128	18,921	38,331	36,604
Tariff Revenue [Member] | Consumption Charges [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	12,182	11,505	22,342	21,476
Tariff Revenue [Member] | Fixed Fees [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	6,657	6,349	13,394	12,997
Tariff Revenue [Member] | Service Charges [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	15	156	162	333
Tariff Revenue [Member] | DSIC [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	1,267	908	2,418	1,795
Tariff Revenue [Member] | Industrial Wastewater Services [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	7	3	15	3
Non-Tariff Revenue [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	1,300	1,420	2,706	2,821
Non-Tariff Revenue [Member] | Service Line Protection Plans [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	1,079	1,028	2,167	2,079
Non-Tariff Revenue [Member] | Contract Operations [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	213	328	429	656
Non-Tariff Revenue [Member] | Inspection Fees [Member]
Disaggregation of Revenue [Abstract]
Total Operating Revenues	$ 8	$ 64	$ 110	$ 86