Regulatory Matters (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Regulatory matters:
Regulatory asset not accruing carrying costs	$ 78,500,000
Pension and other post-retirement obligations
Regulatory matters:
Regulatory asset not accruing carrying costs	52,600,000
Flow-through taxes, net
Regulatory matters:
Regulatory asset not accruing carrying costs	16,400,000
Memorandum account to track unrealized gains and losses on purchase power contracts
Regulatory matters:
Regulatory asset not accruing carrying costs	3,100,000
GOLDEN STATE WATER COMPANY
Regulatory matters:
Total	176,015,000	179,957,000
GOLDEN STATE WATER COMPANY | Various refunds to customers
Regulatory matters:
Total	(7,558,000)	(12,491,000)
GOLDEN STATE WATER COMPANY | WRAM, net of MCBA
Regulatory matters:
Total	42,574,000	39,112,000
GOLDEN STATE WATER COMPANY | Base revenue requirement adjustment mechanism
Regulatory matters:
Total	6,833,000	4,053,000
GOLDEN STATE WATER COMPANY | Electric supply cost balancing account
Regulatory matters:
Total	5,558,000	8,347,000
GOLDEN STATE WATER COMPANY | Costs deferred for future recovery on Aerojet case
Regulatory matters:
Total	16,030,000	17,173,000
GOLDEN STATE WATER COMPANY | Pension and other post-retirement obligations
Regulatory matters:
Total	56,894,000	56,960,000
GOLDEN STATE WATER COMPANY | Derivative unrealized loss
Regulatory matters:
Total	3,060,000	7,611,000
GOLDEN STATE WATER COMPANY | Flow-through taxes, net
Regulatory matters:
Total	16,415,000	17,032,000
GOLDEN STATE WATER COMPANY | Asset retirement obligations
Regulatory matters:
Total	2,781,000	2,793,000
GOLDEN STATE WATER COMPANY | Low income rate assistance balancing accounts
Regulatory matters:
Total	9,119,000	6,194,000
GOLDEN STATE WATER COMPANY | Other regulatory assets, net
Regulatory matters:
Total	$ 24,309,000	$ 33,173,000