Regulatory Matters: (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Regulatory matters:
Regulatory asset not accruing carrying costs	$ 56,200
Other Liabilities, Current	10,421		$ 10,209
Pension and other post-retirement obligations
Regulatory matters:
Regulatory asset not accruing carrying costs	23,300
Derivative unrealized loss
Regulatory matters:
Regulatory asset not accruing carrying costs	5,581
GOLDEN STATE WATER COMPANY
Regulatory matters:
Regulatory assets	154,092		132,696
Other Liabilities, Current	10,312		9,921
GOLDEN STATE WATER COMPANY | Water Revenue Adjustment Mechanism, net of Modified Cost Balancing Account
Regulatory matters:
Regulatory Asset Amount Billed to Customers as Surcharges	12,900	$ 1,700
Regulatory assets	65,444		45,171
GOLDEN STATE WATER COMPANY | Costs deferred for future recovery on Aerojet case
Regulatory matters:
Regulatory assets	12,037		12,699
GOLDEN STATE WATER COMPANY | Pension and other post-retirement obligations
Regulatory matters:
Regulatory assets	24,835		21,996
GOLDEN STATE WATER COMPANY | Derivative unrealized loss
Regulatory matters:
Regulatory assets			7,053
GOLDEN STATE WATER COMPANY | Flow-through taxes, net
Regulatory matters:
Regulatory assets	17,634		16,176
GOLDEN STATE WATER COMPANY | Low income rate assistance balancing accounts
Regulatory matters:
Regulatory assets	8,378		8,699
GOLDEN STATE WATER COMPANY | Other regulatory assets
Regulatory matters:
Regulatory assets	26,309		25,668
GOLDEN STATE WATER COMPANY | Various refunds to customers
Regulatory matters:
Regulatory assets	$ (6,126)		$ (4,766)