INCOME TAXES (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Developer deposits for extension agreements and contributions in aid of construction	$ 39,074	$ 33,552
Net operating loss carryforward and tax credits	8,257	13,329
Pension liability	8,725	7,906
Income tax regulatory liability	44,072	41,712
Other	4,273	280
Total deferred tax assets	104,401	96,779
Deferred tax liabilities:
Property related basis and depreciation differences	288,544	262,442
WRAM/MCBA and interim rates balancing accounts	26,348	26,404
Other	2,542	2,550
Total deferred tax liabilities	317,434	291,396
Net deferred tax liabilities	213,033	194,617
Reconciliation of the changes in unrecognized tax benefits
Balance at beginning of year	11,058	10,499	$ 10,298
Additions for tax positions taken during prior year	0	0	0
Additions for tax positions taken during current year	1,787
Additions for tax positions taken during current year		559	201
Reduction to prior year tax position	(3,129)	0	0
Lapse of statute of limitations	0	0	0
Balance at end of year	$ 9,716	$ 11,058	$ 10,499