CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income (loss)	$ 48,675	$ 45,017	$ 56,738
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	0	0	0
Dividends received from affiliates	0	0	0
Depreciation and amortization	65,203	63,182	63,322
Amortization of debt premium and expenses	871	825	797
Change in value of life insurance contracts	(1,026)	218	(994)
Stock-based compensation	2,849	2,578	2,195
Loss (gain) on sale of non-utility property	146	(315)	(51)
Write-off of capital costs	3,221
Changes in deferred income taxes	26,818	24,393	34,125
Changes in operating assets and liabilities	6,781	(1,877)	(12,681)
Other changes in noncurrent assets and liabilities	6,162	11,435	(14,521)
Net cash provided by operating activities	159,700	144,631	128,133
Investing activities:
Utility plant expenditures	(228,938)	(176,833)	(132,015)
Proceeds from sale of non-utility assets	395	319	57
Investment in affiliates		0	0
Change in affiliate advances	0	0	0
Reduction of affiliate short-term borrowings	0	0
Life insurance benefits	495	0	0
Issuance of affiliate short-term borrowings	0	0
Reduction of affiliate long-term debt	0	0	0
Purchase of life insurance contracts	(2,857)	(2,032)	(3,207)
Change in restricted cash	66	288	396
Net cash used in investing activities	(230,839)	(178,258)	(134,769)
Financing Activities:
Short-term borrowings	145,100	94,303	117,300
Repayment of short-term borrowings	(81,615)	(141,000)	(85,000)
Investment from affiliates		0	0
Change in affiliate advances	0	0	0
Proceeds from affiliate short-term borrowings	0	0
Reduction of affiliate short-term borrowings	0	0
Repayment of affiliate long-term debt	0	0	0
Issuance of long-term debt, net	49,823	99,343	497
Repayment of long-term debt	(6,996)	(7,003)	(8,705)
Advances and contributions in aid of construction	21,448	16,026	12,329
Refunds of advances for construction	(6,885)	(6,726)	(6,641)
Dividends paid to non-affiliates	(33,081)	(32,066)	(31,063)
Dividends paid to affiliates	0	0	0
Net cash provided by (used in) financing activities	87,794	22,877	(1,283)
Change in cash and cash equivalents	16,655	(10,750)	(7,919)
Cash and cash equivalents at beginning of year	8,837	19,587	27,506
Cash and cash equivalents at end of year	25,492	8,837	19,587
Consolidating Adjustments
Operating activities:
Net income (loss)	(48,101)	(44,456)	(56,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	48,158	44,516	56,064
Dividends received from affiliates	(33,081)	(32,066)	(31,063)
Depreciation and amortization	(96)	(101)	(107)
Amortization of debt premium and expenses	0
Change in value of life insurance contracts	0	0	0
Stock-based compensation	0	0	0
Loss (gain) on sale of non-utility property	0	0	0
Write-off of capital costs	0
Changes in deferred income taxes	0	0	0
Changes in operating assets and liabilities	0	(94)	0
Other changes in noncurrent assets and liabilities	39	135	43
Net cash provided by operating activities	(33,081)	(32,066)	(31,063)
Investing activities:
Utility plant expenditures	0	0	0
Proceeds from sale of non-utility assets	0	0	0
Investment in affiliates		1,000	47,650
Change in affiliate advances	(1,335)	1,235	1,133
Reduction of affiliate short-term borrowings	(42,465)	(3,000)
Life insurance benefits	0
Issuance of affiliate short-term borrowings	22,965	24,780
Reduction of affiliate long-term debt	(1,175)	(1,007)	(938)
Purchase of life insurance contracts	0	0	0
Change in restricted cash	0	0	0
Net cash used in investing activities	(22,010)	23,008	47,845
Financing Activities:
Short-term borrowings	0	0	0
Repayment of short-term borrowings	0	0	0
Investment from affiliates		(1,000)	(47,650)
Change in affiliate advances	1,335	(1,235)	(1,133)
Proceeds from affiliate short-term borrowings	(22,965)	(24,780)
Reduction of affiliate short-term borrowings	42,465	3,000
Repayment of affiliate long-term debt	1,175	1,007	938
Issuance of long-term debt, net	0	0	0
Repayment of long-term debt	0	0	0
Advances and contributions in aid of construction	0	0	0
Refunds of advances for construction	0	0	0
Dividends paid to non-affiliates	0	0	0
Dividends paid to affiliates	33,081	32,066	31,063
Net cash provided by (used in) financing activities	55,091	9,058	(16,782)
Change in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of year	0	0	0
Cash and cash equivalents at end of year	0	0	0
Parent Company
Operating activities:
Net income (loss)	48,675	45,017	56,738
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	(48,158)	(44,516)	(56,064)
Dividends received from affiliates	33,081	32,066	31,063
Depreciation and amortization	220	228	214
Amortization of debt premium and expenses	0
Change in value of life insurance contracts	0	0	0
Stock-based compensation	2,849	2,578	2,195
Loss (gain) on sale of non-utility property	0	0	0
Write-off of capital costs	0
Changes in deferred income taxes	0	0	0
Changes in operating assets and liabilities	(14)	(758)	16
Other changes in noncurrent assets and liabilities	(389)	1,436	789
Net cash provided by operating activities	36,264	36,051	34,951
Investing activities:
Utility plant expenditures	0	0	0
Proceeds from sale of non-utility assets	0	0	0
Investment in affiliates		(1,000)	(47,650)
Change in affiliate advances	291	(239)	(3,200)
Reduction of affiliate short-term borrowings	365	3,000
Life insurance benefits	0
Issuance of affiliate short-term borrowings	(2,365)	(3,280)
Reduction of affiliate long-term debt	1,175	1,007	938
Purchase of life insurance contracts	0	0	0
Change in restricted cash	0	0	0
Net cash used in investing activities	(534)	(512)	(49,912)
Financing Activities:
Short-term borrowings	44,100	15,101	64,900
Repayment of short-term borrowings	(20,615)	(43,600)	(20,000)
Investment from affiliates		0	0
Change in affiliate advances	0	0	(48)
Proceeds from affiliate short-term borrowings	20,600	21,500
Reduction of affiliate short-term borrowings	(42,100)	0
Repayment of affiliate long-term debt	0	0	0
Issuance of long-term debt, net	0	0	0
Repayment of long-term debt	0	0	0
Advances and contributions in aid of construction	0	0	0
Refunds of advances for construction	0	0	0
Dividends paid to non-affiliates	(33,081)	(32,066)	(31,063)
Dividends paid to affiliates	0	0	0
Net cash provided by (used in) financing activities	(31,096)	(39,065)	13,789
Change in cash and cash equivalents	4,634	(3,526)	(1,172)
Cash and cash equivalents at beginning of year	582	4,108	5,280
Cash and cash equivalents at end of year	5,216	582	4,108
Cal Water
Operating activities:
Net income (loss)	45,316	44,056	57,680
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	0	0	0
Dividends received from affiliates	0	0	0
Depreciation and amortization	60,572	58,385	58,657
Amortization of debt premium and expenses	871
Change in value of life insurance contracts	(1,026)	218	(994)
Stock-based compensation	0	0	0
Loss (gain) on sale of non-utility property	146	(315)	(51)
Write-off of capital costs	3,221
Changes in deferred income taxes	26,818	24,393	34,125
Changes in operating assets and liabilities	6,534	(6,417)	(11,803)
Other changes in noncurrent assets and liabilities	4,645	14,807	(15,596)
Net cash provided by operating activities	147,097	135,127	122,018
Investing activities:
Utility plant expenditures	(224,378)	(171,645)	(125,048)
Proceeds from sale of non-utility assets	395	319	57
Investment in affiliates		0	0
Change in affiliate advances	1,111	(1,111)	2,147
Reduction of affiliate short-term borrowings	42,100	0
Life insurance benefits	495
Issuance of affiliate short-term borrowings	(20,600)	(21,500)
Reduction of affiliate long-term debt	0	0	0
Purchase of life insurance contracts	(2,857)	(2,032)	(3,207)
Change in restricted cash	66	288	396
Net cash used in investing activities	(203,668)	(195,681)	(125,655)
Financing Activities:
Short-term borrowings	101,000	79,202	52,400
Repayment of short-term borrowings	(61,000)	(97,400)	(65,000)
Investment from affiliates		0	42,000
Change in affiliate advances	(128)	397	270
Proceeds from affiliate short-term borrowings	0	0
Reduction of affiliate short-term borrowings	0	0
Repayment of affiliate long-term debt	0	0	0
Issuance of long-term debt, net	49,823	99,293	0
Repayment of long-term debt	(6,548)	(6,528)	(6,934)
Advances and contributions in aid of construction	21,329	14,195	11,219
Refunds of advances for construction	(6,855)	(6,681)	(6,529)
Dividends paid to non-affiliates	0	0	0
Dividends paid to affiliates	(32,105)	(31,583)	(30,650)
Net cash provided by (used in) financing activities	65,516	50,895	(3,224)
Change in cash and cash equivalents	8,945	(9,659)	(6,861)
Cash and cash equivalents at beginning of year	4,270	13,929	20,790
Cash and cash equivalents at end of year	13,215	4,270	13,929
All Other Subsidiaries
Operating activities:
Net income (loss)	2,785	400	(1,680)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	0	0	0
Dividends received from affiliates	0	0	0
Depreciation and amortization	4,507	4,670	4,558
Amortization of debt premium and expenses	0
Change in value of life insurance contracts	0	0	0
Stock-based compensation	0	0	0
Loss (gain) on sale of non-utility property	0	0	0
Write-off of capital costs	0
Changes in deferred income taxes	0	0	0
Changes in operating assets and liabilities	261	5,392	(894)
Other changes in noncurrent assets and liabilities	1,867	(4,943)	243
Net cash provided by operating activities	9,420	5,519	2,227
Investing activities:
Utility plant expenditures	(4,560)	(5,188)	(6,967)
Proceeds from sale of non-utility assets	0	0	0
Investment in affiliates		0	0
Change in affiliate advances	(67)	115	(80)
Reduction of affiliate short-term borrowings	0	0
Life insurance benefits	0
Issuance of affiliate short-term borrowings	0	0
Reduction of affiliate long-term debt	0	0	0
Purchase of life insurance contracts	0	0	0
Change in restricted cash	0	0	0
Net cash used in investing activities	(4,627)	(5,073)	(7,047)
Financing Activities:
Short-term borrowings	0	0	0
Repayment of short-term borrowings	0	0	0
Investment from affiliates		1,000	5,650
Change in affiliate advances	(1,207)	838	911
Proceeds from affiliate short-term borrowings	2,365	3,280
Reduction of affiliate short-term borrowings	(365)	(3,000)
Repayment of affiliate long-term debt	(1,175)	(1,007)	(938)
Issuance of long-term debt, net	0	50	497
Repayment of long-term debt	(448)	(475)	(1,771)
Advances and contributions in aid of construction	119	1,831	1,110
Refunds of advances for construction	(30)	(45)	(112)
Dividends paid to non-affiliates	0	0	0
Dividends paid to affiliates	(976)	(483)	(413)
Net cash provided by (used in) financing activities	(1,717)	1,989	4,934
Change in cash and cash equivalents	3,076	2,435	114
Cash and cash equivalents at beginning of year	3,985	1,550	1,436
Cash and cash equivalents at end of year	$ 7,061	$ 3,985	$ 1,550