Regulatory Matters: (Details 2) (GSWC, USD $)	1 Months Ended	3 Months Ended
	Apr. 30, 2012	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Regulatory matters:
Under (over) collection		$ 185,229,000		$ 176,015,000
WRAM, net of MCBA
Regulatory matters:
Commercial paper, term		90 days
Amount billed to customers as surcharges		3,600,000	3,400,000
Under (over) collection		44,449,000		42,574,000
Annual surcharges as a percentage of the last authorized revenue requirement	10.00%
WRAM, net of MCBA | Minimum
Regulatory matters:
Recovery periods		18 months
WRAM, net of MCBA | Maximum
Regulatory matters:
Recovery periods		24 months
Under-collection balances as a percentage of adopted annual revenues	15.00%
Recovery period for under-collection balances that are up to 15% of adopted annual revenues	18 months
WRAM
Regulatory matters:
Under (over) collection		61,900,000
Modified Cost Balancing Account
Regulatory matters:
Under (over) collection		(17,500,000)
Base revenue requirement adjustment mechanism
Regulatory matters:
Under (over) collection		7,270,000		6,833,000
Period of surcharge approved		36 months
Increase in revenue requirement recoverable through surcharges collected		$ 1,600,000