CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Condensed Consolidating Financial Statements
Operating revenue	$ 103,014	$ 169,254	$ 131,397	$ 98,149	$ 105,457	$ 146,349	$ 118,321	$ 90,272	$ 501,814	$ 460,399	$ 449,372
Operations:
Purchased water									142,570	125,930	121,695
Purchased power									30,053	29,577	28,252
Pump taxes									9,130	8,600	9,537
Administrative and general									85,758	75,276	75,243
Other									54,696	56,518	56,577
Maintenance									20,698	19,685	18,537
Depreciation and amortization									50,385	42,828	39,778
Income tax (benefit) expense									23,025	23,069	24,812
Taxes other than income taxes									18,332	17,103	16,822
Total operating expenses									434,647	398,586	391,253
Net operating income	7,586	30,078	19,555	9,948	11,906	25,865	16,284	7,758	67,167	61,813	58,119
Other Income and Expenses:
Non-regulated revenue									16,160	15,993	18,190
Non-regulated expense									(15,822)	(12,312)	(12,452)
Gain on sale of non-utility property									62	22	560
Income tax (expense) on other income and expenses									(141)	(1,487)	(2,550)
Net other income									259	2,216	3,748
Interest:
Interest expense									32,455	27,936	24,394
Less: capitalized interest									2,741	1,563	3,081
Net interest expense									29,714	26,373	21,313
Net income	1,868	20,935	12,190	2,719	4,871	20,386	10,381	2,018	37,712	37,656	40,554
Parent Company
Operations:
Income tax (benefit) expense									(580)	(843)	(222)
Total operating expenses									(580)	(843)	(222)
Net operating income									580	843	222
Other Income and Expenses:
Non-regulated revenue									2,248	1,220	901
Income tax (expense) on other income and expenses									(916)	(497)	(367)
Net other income									1,332	723	534
Interest:
Interest expense									1,422	698	505
Net interest expense									1,422	698	505
Equity earnings of subsidiaries									37,222	36,788	40,303
Net income									37,712	37,656	40,554
Cal Water
Condensed Consolidating Financial Statements
Operating revenue									472,150	430,988	420,412
Operations:
Purchased water									142,355	125,749	121,360
Purchased power									20,719	21,616	21,254
Pump taxes									8,764	8,017	8,982
Administrative and general									77,622	67,536	68,103
Other									47,800	49,356	49,560
Maintenance									19,916	18,998	17,918
Depreciation and amortization									47,872	40,349	37,740
Income tax (benefit) expense									23,727	23,812	23,919
Taxes other than income taxes									15,908	14,904	14,727
Total operating expenses									404,683	370,337	363,563
Net operating income									67,467	60,651	56,849
Other Income and Expenses:
Non-regulated revenue									12,972	10,064	12,408
Non-regulated expense									(12,287)	(7,954)	(7,972)
Gain on sale of non-utility property									62	22	560
Income tax (expense) on other income and expenses									(304)	(869)	(2,036)
Net other income									443	1,263	2,960
Interest:
Interest expense									31,421	27,059	23,719
Less: capitalized interest									(1,844)	(1,085)	(2,359)
Net interest expense									29,577	25,974	21,360
Net income									38,333	35,940	38,449
All Other Subsidiaries
Condensed Consolidating Financial Statements
Operating revenue									29,664	29,411	28,960
Operations:
Purchased water									215	181	335
Purchased power									9,334	7,961	6,998
Pump taxes									366	583	555
Administrative and general									8,136	7,740	7,140
Other									7,401	7,667	7,477
Maintenance									782	687	619
Depreciation and amortization									2,637	2,610	2,176
Income tax (benefit) expense									(1,727)	(229)	398
Taxes other than income taxes									2,424	2,199	2,095
Total operating expenses									29,568	29,399	27,793
Net operating income									96	12	1,167
Other Income and Expenses:
Non-regulated revenue									4,322	6,670	6,379
Non-regulated expense									(3,535)	(4,358)	(4,480)
Income tax (expense) on other income and expenses									(422)	(1,027)	(808)
Net other income									365	1,285	1,091
Interest:
Interest expense									2,489	1,635	1,207
Less: capitalized interest									(897)	(478)	(722)
Net interest expense									1,592	1,157	485
Net income									(1,131)	140	1,773
Consolidating Adjustments
Operations:
Other									(505)	(505)	(460)
Depreciation and amortization									(124)	(131)	(138)
Income tax (benefit) expense									1,605	329	717
Total operating expenses									976	(307)	119
Net operating income									(976)	307	(119)
Other Income and Expenses:
Non-regulated revenue									(3,382)	(1,961)	(1,498)
Income tax (expense) on other income and expenses									1,501	906	661
Net other income									(1,881)	(1,055)	(837)
Interest:
Interest expense									(2,877)	(1,456)	(1,037)
Net interest expense									(2,877)	(1,456)	(1,037)
Equity earnings of subsidiaries									(37,222)	(36,788)	(40,303)
Net income									$ (37,202)	$ (36,080)	$ (40,222)