Income Taxes: (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
GOLDEN STATE WATER COMPANY
Effective income tax rate
ETRs (as a percent)	23.60%	39.80%	21.90%	38.80%
Parent [Member]
Effective income tax rate
ETRs (as a percent)	21.20%	38.60%	20.40%	37.40%