INCOME TAXES (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets:
Developer deposits for extension agreements and contributions in aid of construction	$ 44,530	$ 45,587
Net operating loss	8,437	1,015
Other	3,607	3,449
Total deferred tax assets	56,574	50,051
Deferred tax liabilities:
Utility plant, principally due to depreciation differences	207,642	155,916
WRAM/MCBA balancing accounts	19,533	17,393
Other	3,245	3,645
Total deferred tax liabilities	230,420	176,954
Net deferred tax liabilities	173,846	126,903
Current portion of deferred income tax	15,000	10,535
Reconciliation of the changes in unrecognized tax benefits
Balance at beginning of year	831		831
Lapse of statute of limitations	(831)
Balance at end of year			831
Total amount of penalties and interest accrued	$ (114)	$ 114	$ 114