REGULATORY ASSETS AND LIABILITIES - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Regulatory Assets and Liabilities
Regulatory Assets	$ 257,621	$ 283,620
Regulatory Liabilities	683,717	627,740
Revision of Prior Period, Adjustment
Regulatory Assets and Liabilities
Regulatory Liabilities		414,100
Cost of removal
Regulatory Assets and Liabilities
Regulatory Liabilities	447,356	414,061
Future tax benefits due to customers
Regulatory Assets and Liabilities
Regulatory Liabilities	118,051	131,155
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory Liabilities	88,728	58,678
HCBA
Regulatory Assets and Liabilities
Regulatory Liabilities	3,242	14,318
CEBA
Regulatory Assets and Liabilities
Regulatory Liabilities	1,200	6,036
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities
Regulatory Liabilities	2,071	172
Other components of net periodic benefit cost
Regulatory Assets and Liabilities
Regulatory Liabilities	10,348	2,475
RSF regulatory liability
Regulatory Assets and Liabilities
Regulatory Liabilities	2,116	0
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory Liabilities	1,633	845
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory Assets	158,486	143,546
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory Assets	25,363	24,946
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets	10,738	41,558
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory Assets	26,686	24,548
Tank coating
Regulatory Assets and Liabilities
Regulatory Assets	19,602	16,395
IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets	3,430	3,682
Recoverable property losses
Regulatory Assets and Liabilities
Regulatory Assets	3,121	3,144
PCBA
Regulatory Assets and Liabilities
Regulatory Assets	4,182	19,091
Regulatory Liabilities	8,972	0
General district balancing account receivable
Regulatory Assets and Liabilities
Regulatory Assets	$ 390	377
Customer assistance program (CAP) and Rate support fund (RSF) accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Regulatory Assets	$ 2,459	2,965
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory Assets	$ 3,164	$ 3,368
Minimum | IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Maximum | IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	2 years