Condensed Consolidating Financial Statements (Details2) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Condensed Consolidating Financial Statements
Operating revenue	$ 131,397	$ 118,321	$ 229,546	$ 208,593
Operations:
Water production costs	44,745	41,834	76,703	72,289
Administrative and general	20,554	18,480	41,056	35,924
Other operations	15,738	14,749	30,373	28,315
Maintenance	5,288	5,158	10,487	10,109
Depreciation and amortization	12,373	10,638	24,961	21,430
Income tax (benefit) expense	8,638	7,091	7,397	8,499
Property and other taxes	4,506	4,087	9,066	7,990
Total operating expenses	111,842	102,037	200,043	184,556
Net operating income	19,555	16,284	29,503	24,037
Other Income and Expenses:
Non-regulated revenue	3,739	3,692	8,072	7,113
Non-regulated expense, net	(3,509)	(3,691)	(6,933)	(7,237)
Gain on sale of non-utility property	62		62
Income tax benefit (expense) on other income and expense	(112)		(478)	60
Net other income (expense)	180	1	723	(64)
Interest:
Interest expense	8,061	6,939	16,549	13,428
Less: capitalized interest	(516)	(1,035)	(1,232)	(1,854)
Net interest expense	7,545	5,904	15,317	11,574
Net income	12,190	10,381	14,909	12,399
California Water Service Group
Operations:
Depreciation and amortization	(5)
Income tax (benefit) expense	(140)	(71)	(292)	(95)
Total operating expenses	(145)	(71)	(292)	(95)
Net operating income	145	71	292	95
Other Income and Expenses:
Non-regulated revenue	566	290	1,089	530
Income tax benefit (expense) on other income and expense	(231)	(172)	(444)	(216)
Net other income (expense)	335	174	645	314
Interest:
Interest expense	350	174	717	234
Net interest expense	350	174	717	234
Equity earnings of subsidiaries	12,060	10,312	14,689	12,224
Net income	12,190	10,381	14,909	12,399
Cal Water
Condensed Consolidating Financial Statements
Operating revenue	123,879	111,376	215,554	194,989
Operations:
Water production costs	42,203	39,556	72,091	68,023
Administrative and general	18,679	16,581	37,223	32,021
Other operations	14,011	12,954	26,995	24,727
Maintenance	5,110	4,951	10,150	9,756
Depreciation and amortization	11,763	10,113	23,692	20,280
Income tax (benefit) expense	8,632	7,134	7,611	8,622
Property and other taxes	3,936	3,567	7,968	6,948
Total operating expenses	104,334	94,856	185,730	170,377
Net operating income	19,545	16,520	29,824	24,612
Other Income and Expenses:
Non-regulated revenue	2,705	2,313	5,727	4,772
Non-regulated expense, net	(2,559)	(2,593)	(4,810)	(5,175)
Gain on sale of non-utility property	62		62
Income tax benefit (expense) on other income and expense	(85)	(171)	(399)	164
Net other income (expense)	123	6,730	580	(239)
Interest:
Interest expense	7,814	6,730	16,036	13,099
Less: capitalized interest	(333)	(706)	(864)	(1,260)
Net interest expense	7,481	6,024	15,172	11,839
Net income	12,187	10,325	15,232	12,534
All Other Subsidiaries
Condensed Consolidating Financial Statements
Operating revenue	7,518	6,945	13,992	13,604
Operations:
Water production costs	2,542	2,278	4,612	4,266
Administrative and general	1,875	1,899	3,833	3,903
Other operations	1,853	2,049	3,632	3,842
Maintenance	178	207	337	353
Depreciation and amortization	646	590	1,331	1,215
Income tax (benefit) expense	(244)	(381)	(690)	(437)
Property and other taxes	570	520	1,098	1,042
Total operating expenses	7,420	7,162	14,153	14,184
Net operating income	98	(217)	(161)	(580)
Other Income and Expenses:
Non-regulated revenue	1,319	1,560	2,917	2,714
Non-regulated expense, net	(950)	(1,098)	(2,123)	(2,062)
Income tax benefit (expense) on other income and expense	(173)	(271)	(377)	(270)
Net other income (expense)	196	379	417	382
Interest:
Interest expense	622	379	1,204	745
Less: capitalized interest	(183)	(329)	(368)	(594)
Net interest expense	439	50	836	151
Net income	(145)	4	(580)	(349)
Consolidating Adjustments
Operations:
Other operations	(126)	(254)	(254)	(254)
Depreciation and amortization	(31)	(65)	(62)	(65)
Income tax (benefit) expense	390	409	768	409
Total operating expenses	233	90	452	90
Net operating income	(233)	(90)	(452)	(90)
Other Income and Expenses:
Non-regulated revenue	(851)	(471)	(1,661)	(903)
Income tax benefit (expense) on other income and expense	377	(271)	742	382
Net other income (expense)	(474)	(344)	(919)	(521)
Interest:
Interest expense	(725)	(344)	(1,408)	(650)
Net interest expense	(725)	(344)	(1,408)	(650)
Equity earnings of subsidiaries	(12,060)	(10,312)	(14,689)	(12,224)
Net income	$ (12,042)	$ (10,329)	$ (14,652)	$ (12,185)