COMMITMENTS AND CONTINGENCIES - Narrative (Details)		12 Months Ended
	Dec. 20, 2017 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2017 well	Dec. 31, 2020 USD ($)
Long-term purchase commitments - other disclosures
Operating lease renewal term		25 years
Finance lease renewal term		25 years
Contingency loss recognized liability				$ 3,500,000
Minimum
Long-term purchase commitments - other disclosures
Operating lease term		1 year
Finance lease term		1 year
Maximum
Long-term purchase commitments - other disclosures
Operating lease term		50 years
Finance lease term		50 years
Kern County Water Agency (Agency)
Long-term purchase commitments - other disclosures
Total capital facilities charge and treated water charge obligation per acre foot		$ 517.91
Portion of estimated operating cost per acre foot for treated water delivered		$ 85.65
California Water Service Company and City of Bakersfield v. The Dow Chemical Company, et al., Civil Case No. CIV-470999 (TCP Action)
Long-term purchase commitments - other disclosures
Amount awarded	$ 85,000,000
Proceeds from legal settlements	$ 56,000,000
Loss Contingency, Claims Settled, Number | well			47
Loss Contingency, Pending Claims, Number | well			57
Loss Contingency, Claims Dismissed, Number | well			36