Regulatory Matters: (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Regulatory matters:
Regulatory asset not accruing carrying costs	$ (23,100)
Regulatory assets	(23,738)	$ (16,539)
Pension and other post-retirement obligations
Regulatory matters:
Regulatory asset not accruing carrying costs	(64,100)
Deferred Income Tax Charge
Regulatory matters:
Regulatory asset not accruing carrying costs	(77,700)
Flow-through taxes, net
Regulatory matters:
Regulatory asset not accruing carrying costs	(7,900)
Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Increase (Decrease) in Other Regulatory Assets	8,700
Derivative unrealized (gain) loss
Regulatory matters:
Regulatory asset not accruing carrying costs	(2,800)
Bear Valley Electric Service, Inc.
Regulatory matters:
Regulatory asset CEMA - Storm	455
Regulatory asset-Wildfire mitigation Plans ( WMP)	1,900
Bear Valley Electric Service, Inc. | Other Regulatory Assets Net [Member]
Regulatory matters:
Regulatory assets	(3,297)	(2,629)
Bear Valley Electric Service, Inc. | Derivative unrealized (gain) loss
Regulatory matters:
Regulatory assets	2,810	(1,537)
Golden State Water Company
Regulatory matters:
Regulatory assets	(23,251)	(12,373)
Golden State Water Company | Revenue Subject to Refund [Member]
Regulatory matters:
Regulatory assets	4,187	4,577
Golden State Water Company | Costs deferred for future recovery on Aerojet case
Regulatory matters:
Regulatory assets	(6,116)	(6,751)
Golden State Water Company | Pension and other post-retirement obligations
Regulatory matters:
Regulatory assets	(63,809)	(65,576)
Golden State Water Company | Catastrophic Event Memo Account (CEMA) [Member]
Regulatory matters:
Regulatory assets	(6,226)	(4,119)
Golden State Water Company | Deferred Income Tax Charge
Regulatory matters:
Regulatory assets	73,668	74,185
Golden State Water Company | Flow-through taxes, net
Regulatory matters:
Regulatory assets	7,323	9,722
Golden State Water Company | Other Regulatory Assets Net [Member]
Regulatory matters:
Regulatory assets	(11,491)	(10,670)
Golden State Water Company | Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Regulatory assets	(20,787)	$ (13,741)
Golden State Water Company | Water Revenue Adjustment Mechanism [Member]
Regulatory matters:
Regulatory assets	(4,400)
Golden State Water Company and Bear Valley Electric Service Inc.
Regulatory matters:
Regulatory asset-CEMA	$ 6,700
Maximum [Member] | Golden State Water Company | Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Regulatory Asset Recovery Periods	24 months
Minimum [Member] | Golden State Water Company | Water Revenue Adjustment Mechanism and Modified Cost Balancing Account
Regulatory matters:
Regulatory Asset Recovery Periods	12 months