Regulatory Matters: (Details 3) (GSWC, USD $)	3 Months Ended
	Mar. 31, 2013 item	Dec. 31, 2012
Regulatory matters:
Regulatory assets	$ 185,229,000	$ 176,015,000
General rate case memorandum accounts
Regulatory matters:
Regulatory assets	11,427,000	4,495,000
Number of water regions	3
Increase (decrease) to net regulatory assets due to settlement of rate case during the period	7,300,000
WRAM, net of MCBA
Regulatory matters:
Regulatory assets	44,449,000	42,574,000
Other regulatory assets, net
Regulatory matters:
Regulatory assets	40,280,000	40,332,000
Increase (decrease) to net regulatory assets due to settlement of rate case during the period	$ 3,200,000