Contingencies (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($) customer	Dec. 31, 2019 USD ($)
Contingencies
Loss Contingency Number of Customers Served | customer	2,900
Proceeds from Sale of Other Assets	$ 34.3
Gain (Loss) on Disposition of Assets	$ 8.3
Term estimate for the environmental cleanup		2 years
Environmental Clean-Up and Remediation | GSWC
Contingencies
Amount spent in clean-up and remediation activities		$ 6.3
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		$ 1.3