INCOME TAXES (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Developer deposits for extension agreements and contributions in aid of construction	$ 25,114	$ 39,074
Net operating loss carryforward and tax credits	11,029	8,257
Pension liability	10,095	8,725
Income tax regulatory liability	47,196	44,072
Operating leases liabilities	4,024
Other	2,975	4,273
Total deferred tax assets	100,433	104,401
Deferred tax liabilities:
Property related basis and depreciation differences	297,470	288,544
WRAM/MCBA and interim rates balancing accounts	17,771	26,348
Operating lease-right to use asset	4,030
Operating lease-right to use asset	14,402
Other	3,752	2,542
Total deferred tax liabilities	323,023	317,434
Net deferred tax liabilities	222,590	213,033
Reconciliation of the changes in unrecognized tax benefits
Balance at beginning of year	9,716	11,058	$ 10,499
Additions for tax positions taken during current year	1,292
Additions for tax positions taken during current year		1,787	559
Reduction to prior year tax position	0	(3,129)	0
Balance at end of year	$ 11,008	$ 9,716	$ 11,058