Regulatory Matters: Alternative-Revenue Programs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Increase (decrease) in other regulatory assets			$ 4,700
GOLDEN STATE WATER COMPANY
Regulatory matters:
Regulatory assets				$ 1,867	$ (2,450)
GOLDEN STATE WATER COMPANY | Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Commercial paper, term			90 days
Amount billed to customers as surcharges	$ 2,200	$ 2,800
Regulatory assets				25,011	$ 22,535
GOLDEN STATE WATER COMPANY | Water Revenue Adjustment Mechanism and Modified Cost Balancing Account | Minimum
Regulatory matters:
Regulatory Asset Recovery Periods			12 months
GOLDEN STATE WATER COMPANY | Water Revenue Adjustment Mechanism and Modified Cost Balancing Account | Maximum
Regulatory matters:
Regulatory Asset Recovery Periods			24 months
GOLDEN STATE WATER COMPANY | Water Revenue Adjustment Mechanism [Member]
Regulatory matters:
Regulatory assets				11,200
GOLDEN STATE WATER COMPANY | Modified Cost Balancing Account
Regulatory matters:
Regulatory assets				$ 13,800