Contingencies: (Details) (GSWC, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 customer	Nov. 04, 2014
Environmental Clean-Up and Remediation
Contingencies
Amount spent in clean-up and remediation activities	4.6
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	1.4
City of Claremont | Condemnation of Properties
Contingencies
Condemnation		135
Number of customers served through water systems	11,000
Ojai FLOW | Condemnation of Properties
Contingencies
Number of customers served through water systems	3,000
City of Apple Valley | Condemnation of Properties
Contingencies
Number of customers served through water systems	2,900
City of Artesia | Condemnation of Properties
Contingencies
Number of customers served through water systems	3,300
Independent Transmission and Distribution System | City of Claremont | Condemnation of Properties
Contingencies
Public Utilities, Property, Plant and Equipment, Net	47.4