SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 6) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 employee	Dec. 31, 2012	Dec. 31, 2011
Regulatory Assets and Liabilities
Regulatory assets	$ 251,681	$ 344,419
Regulatory assets, net long-term receivable	251,681	344,419
Regulatory liabilities	34,251	35,720
Short-term portion of the regulatory assets	30,887	34,020
Short-term portion of the regulatory liabilities	1,827	5,018
Impairment of Long-Lived Assets, Intangibles and Goodwill
Impairment of goodwill	0	0
Long-Term Debt Premium, Discount and Expense
Amortization expense included in interest expense	1,081	1,107	1,082
Advances for Construction
Advances for construction refunded primarily over a 40-year period	182,776	186,753
Refund period	40 years
Other advances for construction refundable based upon customer connections	617	831
Estimated refunds of advances
2014	7,394
2015	7,392
2016	7,330
2017	7,313
2018	7,296
Thereafter	146,668
Collective Bargaining Agreements
Number of employees	1,125
Number of non-supervisory employees represented by the Utility Workers Union of America	703
Future tax benefits due ratepayers
Regulatory Assets and Liabilities
Regulatory liabilities	24,195	24,932
Conservation program
Regulatory Assets and Liabilities
Regulatory liabilities	6,291	6,538
Other liabilities
Regulatory Assets and Liabilities
Regulatory liabilities	3,765	4,250
Pension and retiree group health
Regulatory Assets and Liabilities
Regulatory assets	119,868	223,153
Certain property-related temporary differences
Regulatory Assets and Liabilities
Regulatory assets	60,780	56,991
Other accrued benefits
Regulatory Assets and Liabilities
Regulatory assets	43,061	40,362
Net WRAM and MCBA accounts receivable
Regulatory Assets and Liabilities
Regulatory assets	46,310	46,071
Regulatory assets, net long-term receivable	15,423	12,051
Short-term portion of the regulatory assets	30,887	34,020
Asset retirement obligations, net
Regulatory Assets and Liabilities
Regulatory assets	$ 12,549	$ 11,862