REGULATORY ASSETS AND LIABILITIES - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Regulatory Assets and Liabilities
Regulatory Assets	$ 283,620	$ 285,692
Regulatory Liabilities	213,679	180,428
Future tax benefits due to customers
Regulatory Assets and Liabilities
Regulatory Liabilities	131,155	135,027
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory Liabilities	58,678	27,294
HCBA
Regulatory Assets and Liabilities
Regulatory Liabilities	14,318	9,687
Conservation program
Regulatory Assets and Liabilities
Regulatory Liabilities	6,036	7,206
Net WRAM and MCBA long-term payable
Regulatory Assets and Liabilities
Regulatory Liabilities	172	143
Other components of net periodic benefit cost
Regulatory Assets and Liabilities
Regulatory Liabilities	2,475	353
Other regulatory liabilities
Regulatory Assets and Liabilities
Regulatory Liabilities	845	718
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory Assets	171	17,607
Property-related temporary differences (tax benefits flowed through to customers)
Regulatory Assets and Liabilities
Regulatory Assets	143,546	130,565
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory Assets	24,946	23,280
Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets	41,558	29,789
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory Assets	24,548	22,935
IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Regulatory Assets	3,682	9,032
Tank coating
Regulatory Assets and Liabilities
Regulatory Assets	$ 16,395	13,680
Recoverable property losses
Regulatory Assets and Liabilities
Recovery Period	7 years
Regulatory Assets	$ 3,144	3,843
PCBA
Regulatory Assets and Liabilities
Regulatory Assets	19,091	21,500
Other components of net periodic benefit cost
Regulatory Assets and Liabilities
Regulatory Assets	0	3,342
General district balancing account receivable
Regulatory Assets and Liabilities
Regulatory Assets	$ 377	568
Customer assistance program (CAP) and Rate support fund (RSF) accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Regulatory Assets	$ 2,965	5,991
Other regulatory assets
Regulatory Assets and Liabilities
Regulatory Assets	$ 3,197	$ 3,560
Minimum | Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Minimum | IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	1 year
Maximum | Net WRAM and MCBA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	2 years
Maximum | IRMA long-term accounts receivable
Regulatory Assets and Liabilities
Recovery Period	2 years