Contingencies and Gain on Sale of Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Loss Contingencies [Line Items]
Amount spent in clean-up and remediation activities [Abstract]	$ 1,500
Utility plant	1,218,830	$ 1,204,992	$ 1,137,159
Accounts receivable	19,224	26,127
Total Assets	1,423,664	1,416,734	$ 1,480,268
Advances for construction	(67,364)	(67,465)
Contributions in aid of construction - net	123,715	123,602
GOLDEN STATE WATER COMPANY
Loss Contingencies [Line Items]
Utility plant	1,209,299	1,197,940
Accounts receivable	19,224	26,127
Regulatory assets	(4,728)	2,042
Total Assets	1,324,556	1,326,823
Advances for construction	(67,364)	(67,465)
Contributions in aid of construction - net	123,715	$ 123,602
Environmental Clean-Up and Remediation | GOLDEN STATE WATER COMPANY
Loss Contingencies [Line Items]
Environmental Remediation Expense	5,500
Accrued liability for the estimated additional cost to complete the clean-up at the site	$ 1,300