CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net income (loss)	$ 48,828	$ 37,712	$ 37,656
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	56,866	51,981	45,265
Change in value of life insurance contracts	(2,504)	1,876	(2,641)
Gain on sale of non-utility property	(84)	(62)	(22)
Changes in deferred income taxes	34,133	2,723
Other changes in noncurrent assets and liabilities	(7,383)	1,693	(160)
Changes in operating assets and liabilities:
Other changes, net	2,058	15,349	(4,588)
Net adjustments	83,086	73,560	37,854
Net cash provided by operating activities	131,914	111,272	75,510
Investing activities:
Utility plant expenditures	(127,681)	(118,546)	(123,926)
Proceeds from sale of non-utility assets	85	64	34
Purchase of life insurance	(3,294)	(1,744)	(1,891)
Restricted cash increase (decrease)	1,959	(3,042)	3,169
Net cash used in investing activities	(128,931)	(123,268)	(122,614)
Financing activities:
Short-term borrowings	94,335	23,390	85,750
Repayment of short-term borrowings	(52,000)		(74,000)
Proceeds from long-term debt, net of issuance cost	124	178	106,173
Retirement of long-term debt	(7,037)	(2,963)	(13,692)
Advances and contributions in aid for construction	6,966	7,231	5,313
Refunds of advances for construction	(7,397)	(6,205)	(6,188)
Dividends paid to non-affiliates	(26,387)	(25,674)	(24,753)
Issuance of common stock		965	912
Net cash provided by (used in) financing activities	8,604	(3,078)	79,515
Change in cash and cash equivalents	11,587	(15,074)	32,411
Cash and cash equivalents at beginning of year	27,203	42,277	9,866
Cash and cash equivalents at end of year	38,790	27,203	42,277
Parent Company
Operating activities:
Net income (loss)	48,828	37,712	37,656
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	(48,538)	(37,222)	(36,788)
Dividends received from affiliates	26,387	25,674	24,753
Depreciation and amortization	56	51
Other changes in noncurrent assets and liabilities	1,544	1,001	229
Changes in operating assets and liabilities:
Other changes, net	(170)	582	(1,054)
Net adjustments	(20,721)	(9,914)	(12,860)
Net cash provided by operating activities	28,107	27,798	24,796
Investing activities:
Utility plant expenditures	(281)		(324)
Affiliate advances	(12,245)	(25,495)	(14,579)
Proceeds from affiliate loans	552
Reduction of loans to affiliates	(5,675)	962	1,854
Net cash used in investing activities	(17,649)	(24,533)	(13,049)
Financing activities:
Short-term borrowings	18,335	23,390	16,750
Repayment of short-term borrowings	(1,000)		(5,000)
Affiliate advances	23
Reduction of affiliate long-term borrowings	(48)	(2,045)
Dividends paid to non-affiliates	(26,387)	(25,674)	(24,753)
Issuance of common stock		965	912
Net cash provided by (used in) financing activities	(9,077)	(3,364)	(12,091)
Change in cash and cash equivalents	1,381	(99)	(344)
Cash and cash equivalents at beginning of year	89	188	532
Cash and cash equivalents at end of year	1,470	89	188
Cal Water
Operating activities:
Net income (loss)	48,772	38,333	35,940
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	54,040	49,283	42,680
Change in value of life insurance contracts	(2,504)	1,876	(2,641)
Gain on sale of non-utility property	(81)	(62)	(22)
Changes in deferred income taxes	34,133	2,723
Other changes in noncurrent assets and liabilities	(10,367)	(45)	(880)
Changes in operating assets and liabilities:
Other changes, net	9,035	11,662	(997)
Net adjustments	84,256	65,437	38,140
Net cash provided by operating activities	133,028	103,770	74,080
Investing activities:
Utility plant expenditures	(111,636)	(98,410)	(108,990)
Proceeds from sale of non-utility assets	82	64	34
Affiliate advances	254	1,597	85
Proceeds from affiliate loans	48
Reduction of loans to affiliates		45
Purchase of life insurance	(3,294)	(1,744)	(1,891)
Restricted cash increase (decrease)	1,959	(3,042)	3,169
Net cash used in investing activities	(112,587)	(101,490)	(107,593)
Financing activities:
Short-term borrowings	76,000		69,000
Repayment of short-term borrowings	(51,000)		(69,000)
Affiliate advances	962
Proceeds from long-term debt, net of issuance cost			103,947
Retirement of long-term debt	(6,310)	(2,279)	(12,212)
Advances and contributions in aid for construction	6,883	7,082	4,962
Refunds of advances for construction	(7,275)	(6,129)	(6,104)
Dividends paid to affiliates	(23,567)	(22,925)	(22,634)
Net cash provided by (used in) financing activities	(4,307)	(24,251)	67,959
Change in cash and cash equivalents	16,134	(21,971)	34,446
Cash and cash equivalents at beginning of year	18,475	40,446	6,000
Cash and cash equivalents at end of year	34,609	18,475	40,446
All Other Subsidiaries
Operating activities:
Net income (loss)	(306)	(1,131)	140
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	2,888	2,771	2,716
Other changes in noncurrent assets and liabilities	1,307	684	1,089
Changes in operating assets and liabilities:
Other changes, net	(6,723)	3,054	(2,558)
Net adjustments	(2,528)	6,509	1,247
Net cash provided by operating activities	(2,834)	5,378	1,387
Investing activities:
Utility plant expenditures	(15,761)	(20,136)	(14,612)
Affiliate advances	(853)
Reduction of loans to affiliates		2,000
Net cash used in investing activities	(16,614)	(18,136)	(14,612)
Financing activities:
Affiliate advances	11,859	23,898	14,494
Proceeds from affiliates long-term borrowings	5,675
Reduction of affiliate long-term borrowings	(552)	(962)	(1,854)
Proceeds from long-term debt, net of issuance cost	124	178	2,226
Retirement of long-term debt	(727)	(684)	(1,480)
Advances and contributions in aid for construction	83	149	351
Refunds of advances for construction	(122)	(76)	(84)
Dividends paid to affiliates	(2,820)	(2,749)	(2,119)
Net cash provided by (used in) financing activities	13,520	19,754	11,534
Change in cash and cash equivalents	(5,928)	6,996	(1,691)
Cash and cash equivalents at beginning of year	8,639	1,643	3,334
Cash and cash equivalents at end of year	2,711	8,639	1,643
Consolidating Adjustments
Operating activities:
Net income (loss)	(48,466)	(37,202)	(36,080)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	48,538	37,222	36,788
Dividends received from affiliates	(26,387)	(25,674)	(24,753)
Depreciation and amortization	(118)	(124)	(131)
Gain on sale of non-utility property	(3)
Other changes in noncurrent assets and liabilities	133	53	(598)
Changes in operating assets and liabilities:
Other changes, net	(84)	51	21
Net adjustments	22,079	11,528	11,327
Net cash provided by operating activities	(26,387)	(25,674)	(24,753)
Investing activities:
Utility plant expenditures	(3)
Proceeds from sale of non-utility assets	3
Affiliate advances	12,844	23,898	14,494
Proceeds from affiliate loans	(600)
Reduction of loans to affiliates	5,675	(3,007)	(1,854)
Net cash used in investing activities	17,919	20,891	12,640
Financing activities:
Affiliate advances	(12,844)	(23,898)	(14,494)
Proceeds from affiliates long-term borrowings	(5,675)
Reduction of affiliate long-term borrowings	600	3,007	1,854
Dividends paid to affiliates	26,387	25,674	24,753
Net cash provided by (used in) financing activities	$ 8,468	$ 4,783	$ 12,113