INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Developer deposits for contributions in aid of construction	$ 31,777	$ 29,491
Net operating loss carryforward and tax credits	24,908	37,326
Pension liability	13,570	12,031
Income tax regulatory liability	26,565	41,151
Operating leases liabilities	4,310	4,372
Other	2,439	2,812
Total deferred tax assets	103,569	127,183
Deferred tax liabilities:
Property related basis and depreciation differences	362,139	350,923
WRAM/MCBA and interim rates balancing accounts	22,124	39,107
Operating lease-right to use asset	4,286	4,362
Other	13,965	8,823
Total deferred tax liabilities	402,514	403,215
Net deferred tax liabilities	$ 298,945	$ 276,032