Condensed Consolidating Financial Statements (Details 4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating activities:
Net income	$ 25,120	$ 33,650	$ 36,540	$ 45,344
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	0	0	0	0
Dividends received from affiliates			0	0
Depreciation and amortization			47,406	48,481
Change in value of life insurance contracts			758	(501)
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			33,476	(6,497)
Other changes in noncurrent assets and liabilities			(1,656)	13,340
Net cash provided by operating activities			116,524	100,167
Investing activities:
Utility plant expenditures			(118,309)	(86,258)
Investment in affiliates			0	0
Changes in affiliate advances			0	0
Proceeds from affiliates long-term debt			0	0
Purchase of life insurance contracts			(1,855)	(3,207)
Change in restricted cash			(241)	354
Net cash used in investing activities			(120,405)	(89,111)
Financing Activities:
Short-term borrowings			82,500	99,900
Repayment of short-term borrowings			(25,000)	(85,000)
Debt issuance costs			(1,197)	0
Investment from affiliates			0	0
Changes in affiliate advances			0	0
Repayment of affiliates long-term borrowings			0	0
Proceeds from long-term debt			50	0
Repayment of long-term debt			(2,878)	(4,604)
Advances and contributions in aid of construction			10,741	8,780
Refunds of advances for construction			(5,050)	(4,858)
Dividends paid to non-affiliates			(24,047)	(23,295)
Dividends paid to affiliates			0	0
Net cash provided by (used in) financing activities			35,119	(9,077)
Change in cash and cash equivalents			31,238	1,979
Cash and cash equivalents at beginning of period			19,587	27,506
Cash and cash equivalents at end of period	50,825	29,485	50,825	29,485
Consolidating Adjustments
Operating activities:
Net income	(24,997)	(33,484)	(36,123)	(44,756)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	25,012	33,499	36,168	44,803
Dividends received from affiliates			(24,047)	(23,295)
Depreciation and amortization			(76)	(80)
Change in value of life insurance contracts			0	$ 0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			125
Other changes in noncurrent assets and liabilities			(94)	$ 33
Net cash provided by operating activities			(24,047)	(23,295)
Investing activities:
Utility plant expenditures			0	0
Investment in affiliates			1,000	46,850
Changes in affiliate advances			280	877
Proceeds from affiliates long-term debt			(767)	(699)
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			513	47,028
Financing Activities:
Short-term borrowings			0	0
Repayment of short-term borrowings			0	0
Investment from affiliates			(1,000)	(46,850)
Changes in affiliate advances			(280)	(877)
Repayment of affiliates long-term borrowings			767	699
Proceeds from long-term debt			0
Repayment of long-term debt			0	0
Advances and contributions in aid of construction			0	0
Refunds of advances for construction			0	0
Dividends paid to non-affiliates			0	0
Dividends paid to affiliates			24,047	23,295
Net cash provided by (used in) financing activities			23,534	(23,733)
Change in cash and cash equivalents			0	0
Cash and cash equivalents at beginning of period			0	0
Cash and cash equivalents at end of period	0	0	0	0
Parent Company
Operating activities:
Net income	25,120	33,650	36,540	45,344
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	(25,012)	(33,499)	(36,168)	(44,803)
Dividends received from affiliates			24,047	23,295
Depreciation and amortization			171	157
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			3,030	(68)
Other changes in noncurrent assets and liabilities			(910)	2,160
Net cash provided by operating activities			26,710	26,085
Investing activities:
Utility plant expenditures			0	0
Investment in affiliates			(1,000)	(46,850)
Changes in affiliate advances			(3,116)	(5,455)
Proceeds from affiliates long-term debt			767	699
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(3,349)	(51,606)
Financing Activities:
Short-term borrowings			2,500	64,900
Repayment of short-term borrowings			0	(20,000)
Debt issuance costs			(399)
Investment from affiliates			0	0
Changes in affiliate advances			0	(48)
Repayment of affiliates long-term borrowings			0	0
Proceeds from long-term debt			0
Repayment of long-term debt			0	0
Advances and contributions in aid of construction			0	0
Refunds of advances for construction			0	0
Dividends paid to non-affiliates			(24,047)	$ (23,295)
Dividends paid to affiliates			0
Net cash provided by (used in) financing activities			(21,946)	$ 21,557
Change in cash and cash equivalents			1,415	(3,964)
Cash and cash equivalents at beginning of period			4,108	5,280
Cash and cash equivalents at end of period	5,523	1,316	5,523	1,316
Cal Water
Operating activities:
Net income	23,984	32,558	35,570	45,560
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	0	0	0	0
Dividends received from affiliates			0	0
Depreciation and amortization			43,768	45,059
Change in value of life insurance contracts			758	(501)
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			35,324	(7,969)
Other changes in noncurrent assets and liabilities			(9,088)	11,539
Net cash provided by operating activities			106,332	93,688
Investing activities:
Utility plant expenditures			(114,325)	(81,505)
Investment in affiliates			0	0
Changes in affiliate advances			2,918	4,778
Proceeds from affiliates long-term debt			0	0
Purchase of life insurance contracts			(1,855)	(3,207)
Change in restricted cash			(241)	354
Net cash used in investing activities			(113,503)	(79,580)
Financing Activities:
Short-term borrowings			80,000	35,000
Repayment of short-term borrowings			(25,000)	(65,000)
Debt issuance costs			(798)
Investment from affiliates			0	42,000
Changes in affiliate advances			2,965	$ 1,814
Repayment of affiliates long-term borrowings			0
Proceeds from long-term debt			0
Repayment of long-term debt			(2,480)	$ (2,919)
Advances and contributions in aid of construction			10,682	8,239
Refunds of advances for construction			(5,014)	(4,809)
Dividends paid to non-affiliates			0	0
Dividends paid to affiliates			(23,754)	(23,005)
Net cash provided by (used in) financing activities			36,601	(8,680)
Change in cash and cash equivalents			29,430	5,428
Cash and cash equivalents at beginning of period			13,929	20,790
Cash and cash equivalents at end of period	43,359	26,218	43,359	26,218
All Other Subsidiaries
Operating activities:
Net income	1,013	926	553	(804)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	0	0	0	0
Dividends received from affiliates			0	0
Depreciation and amortization			3,543	3,345
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			(5,003)	1,540
Other changes in noncurrent assets and liabilities			8,436	(392)
Net cash provided by operating activities			7,529	3,689
Investing activities:
Utility plant expenditures			(3,984)	(4,753)
Investment in affiliates			0	0
Changes in affiliate advances			(82)	(200)
Proceeds from affiliates long-term debt			0	0
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(4,066)	(4,953)
Financing Activities:
Short-term borrowings			0	0
Repayment of short-term borrowings			0	0
Debt issuance costs			0
Investment from affiliates			1,000	4,850
Changes in affiliate advances			(2,685)	(889)
Repayment of affiliates long-term borrowings			(767)	(699)
Proceeds from long-term debt			50
Repayment of long-term debt			(398)	(1,685)
Advances and contributions in aid of construction			59	541
Refunds of advances for construction			(36)	(49)
Dividends paid to non-affiliates			0	0
Dividends paid to affiliates			(293)	(290)
Net cash provided by (used in) financing activities			(3,070)	1,779
Change in cash and cash equivalents			393	515
Cash and cash equivalents at beginning of period			1,550	1,436
Cash and cash equivalents at end of period	$ 1,943	$ 1,951	$ 1,943	$ 1,951