Contingencies: (Details) - GSWC $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($) customer	Nov. 04, 2014 USD ($)
Environmental Clean-Up and Remediation
Contingencies
Amount spent in clean-up and remediation activities	$ 4.8
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		$ 135.0
Number of customers served through water systems | customer	11,000
Ojai FLOW | Condemnation of Properties
Contingencies
Number of customers served through water systems | customer	3,000
City of Artesia | Condemnation of Properties
Contingencies
Number of customers served through water systems | customer	3,300
Independent Transmission and Distribution System | City of Claremont | Condemnation of Properties
Contingencies
Public Utilities, Property, Plant and Equipment, Net	$ 49.8