Contingencies: (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended	36 Months Ended	3 Months Ended
	Mar. 08, 2013 Barstow Perchlorate Contamination item	Mar. 31, 2013 Condemnation of Properties GSWC	Dec. 31, 2012 Condemnation of Properties GSWC item	Mar. 31, 2013 Environmental Clean-Up and Remediation GSWC	Mar. 31, 2013 Environmental Clean-Up and Remediation GSWC Minimum	Mar. 31, 2013 City of Claremont Condemnation of Properties GSWC customer	Mar. 31, 2013 Ojai FLOW Condemnation of Properties GSWC customer	Mar. 31, 2013 Santa Maria Valley Water Conservation District GSWC acrefeet
Contingencies
Number of toxic tort lawsuit served	4
Number of active production wells for which lawsuits served	1
Number of customers served through water systems						11,000	3,000
Number of formal condemnation proceedings filed			0
Period during which no formal condemnation proceedings were filed		3 years
Area of groundwater replenishment provided (in acre-feet)								10,000
Percentage of the return flows generated from importation of state water project to be recaptured								45.00%
Estimated period for remediation				2 years
Period of monitoring and reporting followed by remediation					1 year
Amount spent in clean-up and remediation activities				$ 3.5
Amount paid by the State of California Underground Storage Tank Fund for clean-up and remediation of plant facilities				1.5
Accrued liability for the estimated additional cost to complete the clean-up at the site				$ 1.2