INCOME TAXES (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Developer deposits for extension agreements and contributions in aid of construction	$ 44,775	$ 44,592
Net operating loss carryforward and tax credits	19,866	9,095
Other	8,904	4,330
Total deferred tax assets	73,545	58,017
Deferred tax liabilities:
Utility plant, principally due to depreciation differences	272,958	231,141
WRAM/MCBA and interim rates balancing accounts	30,871	18,556
Other	4,308	3,789
Total deferred tax liabilities	308,137	253,486
Net deferred tax liabilities	234,592	195,469
Current portion of deferred income tax	19,750	12,224
Reconciliation of the changes in unrecognized tax benefits
Balance at beginning of year	612		831
Additions for tax positions taken during current year	7,304	612
Lapse of statute of limitations			(831)
Balance at end of year	$ 7,916	$ 612