CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Condensed Consolidating Financial Statements
Net cash provided by operating activities	$ 111,272	$ 75,510	$ 72,424
Net cash provided by (used in) investing activities	(123,268)	(122,614)	(114,715)
Net cash (used in) provided by financing activities	(3,078)	79,515	38,288
Parent Company
Condensed Consolidating Financial Statements
Net cash provided by operating activities	27,798	24,796	23,712
Net cash provided by (used in) investing activities	(24,533)	(13,049)	255
Net cash (used in) provided by financing activities	(3,364)	(12,091)	(23,862)
Parent Company | As previously reported
Condensed Consolidating Financial Statements
Net cash provided by operating activities		10,217	23,552
Net cash provided by (used in) investing activities		1,530	415
Net cash (used in) provided by financing activities		(12,091)	(23,862)
Cal Water
Condensed Consolidating Financial Statements
Net cash provided by operating activities	103,770	74,080	67,842
Net cash provided by (used in) investing activities	(101,490)	(107,593)	(105,328)
Net cash (used in) provided by financing activities	(24,251)	67,959	40,461
Cal Water | As previously reported
Condensed Consolidating Financial Statements
Net cash provided by operating activities		74,165	66,803
Net cash provided by (used in) investing activities		(107,678)	(104,289)
Net cash (used in) provided by financing activities		67,959	40,461
All Other Subsidiaries
Condensed Consolidating Financial Statements
Net cash provided by operating activities	5,378	1,387	5,346
Net cash provided by (used in) investing activities	(18,136)	(14,612)	(10,426)
Net cash (used in) provided by financing activities	19,754	11,534	2,003
All Other Subsidiaries | As previously reported
Condensed Consolidating Financial Statements
Net cash provided by operating activities		15,881	6,545
Net cash provided by (used in) investing activities		(14,612)	(10,426)
Net cash (used in) provided by financing activities		(2,960)	(3,202)
Consolidating Adjustments
Condensed Consolidating Financial Statements
Net cash provided by operating activities	(25,674)	(24,753)	(24,476)
Net cash provided by (used in) investing activities	20,891	12,640	784
Net cash (used in) provided by financing activities	4,783	12,113	23,692
Consolidating Adjustments | As previously reported
Condensed Consolidating Financial Statements
Net cash provided by operating activities		(24,753)	(24,476)
Net cash provided by (used in) investing activities		(1,854)	(415)
Net cash (used in) provided by financing activities		$ 26,607	$ 24,891