SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue (Details ) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 905,623	$ 790,334	$ 772,616
Regulatory balancing account revenue	131,183	4,298	73,815
Operating revenue	1,036,806	794,632	846,431
Non-regulated revenue	20,628	18,509	21,276
Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	538,234	463,417	458,448
Business
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	180,032	159,050	153,570
Multiple residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76,835	67,703	64,481
Industrial
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30,399	28,055	26,622
Public authorities
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	49,162	40,811	41,150
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30,961	31,298	28,345
Operating and maintenance revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13,818	12,499	12,860
Other non-regulated revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4,400	3,506	5,774
Non-regulated revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18,218	16,005	18,634
Lease revenue	2,410	2,504	2,642
Non-regulated revenue	$ 20,628	$ 18,509	$ 21,276