Regulatory Matters: (Details) (USD $)	Sep. 30, 2013	May 31, 2013 Base Revenue Requirement Adjustment Mechanism	Sep. 30, 2013 Pension and other post-retirement obligations	Sep. 30, 2013 Flow-through taxes, net	Sep. 30, 2013 Memorandum account to track unrealized gains and losses on purchase power contracts	Sep. 30, 2013 GOLDEN STATE WATER COMPANY	Dec. 31, 2012 GOLDEN STATE WATER COMPANY	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Various refunds to customers	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Various refunds to customers	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Water Revenue Adjustment Mechanism, net of Modified Cost Balancing Account	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Water Revenue Adjustment Mechanism, net of Modified Cost Balancing Account	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Base Revenue Requirement Adjustment Mechanism	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Base Revenue Requirement Adjustment Mechanism	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Costs deferred for future recovery on Aerojet case	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Costs deferred for future recovery on Aerojet case	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Pension and other post-retirement obligations	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Pension and other post-retirement obligations	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Flow-through taxes, net	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Flow-through taxes, net	Sep. 30, 2013 GOLDEN STATE WATER COMPANY General rate case memorandum accounts	Dec. 31, 2012 GOLDEN STATE WATER COMPANY General rate case memorandum accounts	Sep. 30, 2013 GOLDEN STATE WATER COMPANY Other regulatory assets	Dec. 31, 2012 GOLDEN STATE WATER COMPANY Other regulatory assets
Regulatory matters:
Regulatory asset not accruing carrying costs	$ 72,300,000		$ 49,800,000	$ 15,900,000	$ 588,000
Regulatory assets		$ 2,300,000				$ 173,498,000	$ 176,015,000	$ (5,022,000)	$ (7,558,000)	$ 29,223,000	$ 42,574,000	$ 8,600,000	$ 6,833,000	$ 15,106,000	$ 16,030,000	$ 54,834,000	$ 56,894,000	$ 15,901,000	$ 16,415,000	$ 17,381,000	$ 4,495,000	$ 37,475,000	$ 40,332,000