CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income as reported and available to common stockholders	$ 56,738	$ 47,254	$ 48,828
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	63,322	60,250	56,866
Change in value of life insurance contracts	(994)	(1,878)	(2,504)
Stock-based compensation	2,195	1,832	1,442
Gain on sale of non-utility property	(51)		(84)
Changes in deferred income taxes	34,125	9,800	34,133
Other changes in noncurrent assets and liabilities	(14,521)	11,325	(8,825)
Changes in operating assets and liabilities	(12,681)	(4,410)	2,058
Net cash provided by operating activities	128,133	124,173	131,914
Investing activities:
Utility plant expenditures	(132,015)	(122,988)	(127,681)
Proceeds from sale of non-utility assets	57		85
Purchase of life insurance	(3,207)	(3,281)	(3,294)
Restricted cash decrease (increase)	396	1,073	1,959
Net cash used in investing activities	(134,769)	(125,196)	(128,931)
Financing Activities:
Short-term borrowings	117,300	70,615	94,335
Repayment of short-term borrowings	(85,000)	(113,275)	(52,000)
Proceeds from long-term debt, net of issuance cost of $1,857	497	48	124
Repayment of long-term debt	(8,705)	(47,248)	(7,037)
Advances and contributions in aid for construction	12,329	10,563	6,966
Refunds of advances for construction	(6,641)	(6,922)	(7,397)
Dividends paid to non-affiliates	(31,063)	(29,619)	(26,387)
Issuance of common stock		105,577
Issuance of common stock, net		110,688
Net cash (used in) provided by financing activities	(1,283)	(10,261)	8,604
Change in cash and cash equivalents	(7,919)	(11,284)	11,587
Cash and cash equivalents at beginning of period	27,506	38,790	27,203
Cash and cash equivalents at end of period	19,587	27,506	38,790
Consolidating Adjustments
Operating activities:
Net income as reported and available to common stockholders	(56,000)	(46,453)	(48,466)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	56,064	46,519	48,538
Dividends received from affiliates	(31,063)	(29,619)	(26,387)
Depreciation and amortization	(107)	(112)	(118)
Gain on sale of non-utility property			(3)
Other changes in noncurrent assets and liabilities	43	(49)	133
Changes in operating assets and liabilities		95	(84)
Net cash provided by operating activities	(31,063)	(29,619)	(26,387)
Investing activities:
Utility plant expenditures			(3)
Investment in affiliates	47,650	35,000
Proceeds from sale of non-utility assets			3
Changes in affiliate advances	1,133	16,268	12,844
Proceeds from affiliate loans	(938)	(9,023)	(600)
Reduction of loans to affiliates			(5,675)
Net cash used in investing activities	47,845	42,245	17,919
Financing Activities:
Investment from affiliates	(47,650)	35,000
Change in affiliate advances	(1,133)	(16,268)	(12,844)
Proceeds from affiliates long-term borrowings			5,675
Reduction of affiliate long-term borrowings	938	9,023	600
Dividends paid to affiliates	31,063	29,619	26,387
Net cash (used in) provided by financing activities	(16,782)	(12,626)	8,468
Parent Company
Operating activities:
Net income as reported and available to common stockholders	56,738	47,254	48,828
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	(56,064)	(46,519)	(48,538)
Dividends received from affiliates	31,063	29,619	26,387
Depreciation and amortization	214	56	56
Stock-based compensation	2,195	1,832	1,442
Other changes in noncurrent assets and liabilities	789	(76)	102
Changes in operating assets and liabilities	16	544	(170)
Net cash provided by operating activities	34,951	32,710	28,107
Investing activities:
Utility plant expenditures		(712)	(281)
Investment in affiliates	(47,650)	(35,000)
Changes in affiliate advances	(3,200)	(14,903)	(12,245)
Proceeds from affiliate loans	938	1,227	552
Reduction of loans to affiliates			5,675
Net cash used in investing activities	(49,912)	(49,388)	(17,649)
Financing Activities:
Short-term borrowings	64,900	20,615	18,335
Repayment of short-term borrowings	(20,000)	(68,275)	(1,000)
Change in affiliate advances	(48)	(14)	23
Reduction of affiliate long-term borrowings		(7,796)	(48)
Dividends paid to non-affiliates	(31,063)	(29,619)	(26,387)
Issuance of common stock		105,577
Net cash (used in) provided by financing activities	13,789	20,488	(9,077)
Change in cash and cash equivalents	(1,172)	3,810	1,381
Cash and cash equivalents at beginning of period	5,280	1,470	89
Cash and cash equivalents at end of period	4,108	5,280	1,470
Cal Water
Operating activities:
Net income as reported and available to common stockholders	57,680	49,009	48,772
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	58,657	56,670	54,040
Change in value of life insurance contracts	(994)	(1,878)	(2,504)
Gain on sale of non-utility property	(51)		(81)
Changes in deferred income taxes	34,125	9,800	34,133
Other changes in noncurrent assets and liabilities	(15,596)	11,899	(10,367)
Changes in operating assets and liabilities	(11,803)	226	9,035
Net cash provided by operating activities	122,018	125,726	133,028
Investing activities:
Utility plant expenditures	(125,048)	(111,819)	(111,636)
Proceeds from sale of non-utility assets	57		82
Changes in affiliate advances	2,147	(2,575)	254
Proceeds from affiliate loans		7,796	48
Purchase of life insurance	(3,207)	(3,281)	(3,294)
Restricted cash decrease (increase)	396	1,073	1,959
Net cash used in investing activities	(125,655)	(108,806)	(112,587)
Financing Activities:
Short-term borrowings	52,400	50,000	76,000
Repayment of short-term borrowings	(65,000)	(45,000)	(51,000)
Investment from affiliates	42,000	(35,000)
Change in affiliate advances	270	(1,152)	962
Repayment of long-term debt	(6,934)	(46,547)	(6,310)
Advances and contributions in aid for construction	11,219	10,465	6,883
Refunds of advances for construction	(6,529)	(6,814)	(7,275)
Dividends paid to affiliates	(30,650)	(26,691)	(23,567)
Net cash (used in) provided by financing activities	(3,224)	(30,739)	(4,307)
Change in cash and cash equivalents	(6,861)	(13,819)	16,134
Cash and cash equivalents at beginning of period	20,790	34,609	18,475
Cash and cash equivalents at end of period	13,929	20,790	34,609
All Other Subsidiaries
Operating activities:
Net income as reported and available to common stockholders	(1,680)	(2,556)	(306)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	4,558	3,636	2,888
Other changes in noncurrent assets and liabilities	243	(449)	1,307
Changes in operating assets and liabilities	(894)	(5,275)	(6,723)
Net cash provided by operating activities	2,227	(4,644)	(2,834)
Investing activities:
Utility plant expenditures	(6,967)	(10,457)	(15,761)
Changes in affiliate advances	(80)	1,210	(853)
Net cash used in investing activities	(7,047)	(9,247)	(16,614)
Financing Activities:
Investment from affiliates	5,650
Change in affiliate advances	911	17,434	11,859
Proceeds from affiliates long-term borrowings			(5,675)
Reduction of affiliate long-term borrowings	(938)	(1,227)	(552)
Proceeds from long-term debt, net of issuance cost of $1,857	497	48	124
Repayment of long-term debt	(1,771)	(701)	(727)
Advances and contributions in aid for construction	1,110	98	83
Refunds of advances for construction	(112)	(108)	(122)
Dividends paid to affiliates	(413)	(2,928)	(2,820)
Net cash (used in) provided by financing activities	4,934	12,616	13,520
Change in cash and cash equivalents	114	(1,275)	(5,928)
Cash and cash equivalents at beginning of period	1,436	2,711	8,639
Cash and cash equivalents at end of period	$ 1,550	$ 1,436	$ 2,711