Condensed Consolidating Financial Statements (Details 4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Operating activities:
Net income	$ 22,875	$ 25,120	$ 33,585	$ 36,540
Adjustments to reconcile net income to net cash provided by operating activities:
Equity earnings of subsidiaries	0	0	0	0
Dividends received from affiliates			0	0
Depreciation and amortization			48,946	47,406
Change in value of life insurance contracts			(915)	758
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			7,827	(1,656)
Other changes in noncurrent assets and liabilities			33,749	33,476
Net cash provided by operating activities			123,192	116,524
Investing activities:
Utility plant expenditures			(166,406)	(118,309)
Investment in affiliates				0
Changes in affiliate advances			0	0
Reduction of affiliate short-term borrowings			0
Issuance of affiliate short-term borrowings			0
Reduction of affiliates long-term debt			0	0
Life insurance proceeds			495	0
Purchase of life insurance contracts			(2,710)	(1,855)
Change in restricted cash			(685)	(241)
Net cash used in investing activities			(169,306)	(120,405)
Financing Activities:
Short-term borrowings			105,100	82,500
Repayment of short-term borrowings			(81,615)	(25,000)
Debt issuance costs			0	(1,197)
Investment from affiliates			0	0
Changes in affiliate advances			0	0
Repayment of affiliate short-term borrowings			0
Repayment of affiliates long-term borrowings			0	0
Proceeds from long-term debt			49,823	50
Repayment of long-term debt			(2,865)	(2,878)
Advances and contributions in aid of construction			18,186	10,741
Refunds of advances for construction			(5,194)	(5,050)
Dividends paid to non-affiliates			(24,807)	(24,047)
Dividends paid to affiliates			0	0
Net cash provided by financing activities			58,628	35,119
Change in cash and cash equivalents			12,514	31,238
Cash and cash equivalents at beginning of period			8,837	19,587
Cash and cash equivalents at end of period	21,351	50,825	21,351	50,825
Consolidating Adjustments
Operating activities:
Net income	(22,739)	(24,997)	(33,145)	(36,123)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity earnings of subsidiaries	22,753	25,012	33,187	36,168
Dividends received from affiliates			(24,807)	(24,047)
Depreciation and amortization			(72)	(76)
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			54	(94)
Other changes in noncurrent assets and liabilities			(24)	125
Net cash provided by operating activities			(24,807)	(24,047)
Investing activities:
Utility plant expenditures			0	0
Investment in affiliates				1,000
Changes in affiliate advances			(3,143)	280
Reduction of affiliate short-term borrowings			(44,100)
Issuance of affiliate short-term borrowings			25,215
Reduction of affiliates long-term debt			(829)	(767)
Life insurance proceeds			0
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(22,857)	513
Financing Activities:
Short-term borrowings			0	0
Repayment of short-term borrowings			0	0
Debt issuance costs				0
Investment from affiliates			(25,215)	(1,000)
Changes in affiliate advances			3,143	(280)
Repayment of affiliate short-term borrowings			44,100
Repayment of affiliates long-term borrowings			829	767
Proceeds from long-term debt			0	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			24,807	24,047
Net cash provided by financing activities			47,664	23,534
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	22,875	25,120	33,585	36,540
Adjustments to reconcile net income to net cash provided by operating activities:
Equity earnings of subsidiaries	(22,753)	(25,012)	(33,187)	(36,168)
Dividends received from affiliates			24,807	24,047
Depreciation and amortization			171	171
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			1,844	(910)
Other changes in noncurrent assets and liabilities			(250)	3,030
Net cash provided by operating activities			26,970	26,710
Investing activities:
Utility plant expenditures			0	0
Investment in affiliates				(1,000)
Changes in affiliate advances			(957)	(3,116)
Reduction of affiliate short-term borrowings			2,000
Issuance of affiliate short-term borrowings			(4,615)
Reduction of affiliates long-term debt			829	767
Life insurance proceeds			0
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(2,743)	(3,349)
Financing Activities:
Short-term borrowings			44,100	2,500
Repayment of short-term borrowings			(20,615)	0
Debt issuance costs				(399)
Investment from affiliates			20,600	0
Changes in affiliate advances			0	0
Repayment of affiliate short-term borrowings			(42,100)
Repayment of affiliates long-term borrowings			0	0
Proceeds from long-term debt			0	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	(24,047)
Dividends paid to affiliates			(24,807)		$ 0
Net cash provided by financing activities			(22,822)	(21,946)
Change in cash and cash equivalents			1,405	1,415
Cash and cash equivalents at beginning of period			582	4,108
Cash and cash equivalents at end of period	1,987	5,523	1,987	5,523
Cal Water
Operating activities:
Net income	21,025	23,984	30,564	35,570
Adjustments to reconcile net income to net cash provided by operating activities:
Equity earnings of subsidiaries	0	0	0	0
Dividends received from affiliates			0	0
Depreciation and amortization			45,466	43,768
Change in value of life insurance contracts			(915)	758
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			12,552	(9,088)
Other changes in noncurrent assets and liabilities			24,726	35,324
Net cash provided by operating activities			112,393	106,332
Investing activities:
Utility plant expenditures			(163,179)	(114,325)
Investment in affiliates				0
Changes in affiliate advances			4,419	2,918
Reduction of affiliate short-term borrowings			42,100
Issuance of affiliate short-term borrowings			(20,600)
Reduction of affiliates long-term debt			0	0
Life insurance proceeds			495
Purchase of life insurance contracts			(2,710)	(1,855)
Change in restricted cash			(685)	(241)
Net cash used in investing activities			(140,160)	(113,503)
Financing Activities:
Short-term borrowings			61,000	80,000
Repayment of short-term borrowings			(61,000)	(25,000)
Debt issuance costs				(798)
Investment from affiliates			0	0
Changes in affiliate advances			1,367	2,965
Repayment of affiliate short-term borrowings			0
Repayment of affiliates long-term borrowings			0		$ 0
Proceeds from long-term debt			49,823	0
Repayment of long-term debt			(2,516)	(2,480)
Advances and contributions in aid of construction			18,096	10,682
Refunds of advances for construction			(5,172)	(5,014)
Dividends paid to non-affiliates			(24,173)	0
Dividends paid to affiliates			0	(23,754)
Net cash provided by financing activities			37,425	36,601
Change in cash and cash equivalents			9,658	29,430
Cash and cash equivalents at beginning of period			4,270	13,929
Cash and cash equivalents at end of period	13,928	43,359	13,928	43,359
All Other Subsidiaries
Operating activities:
Net income	1,714	1,013	2,581	553
Adjustments to reconcile net income to net cash provided by operating activities:
Equity earnings of subsidiaries	0	0	0	0
Dividends received from affiliates			0	0
Depreciation and amortization			3,381	3,543
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			(6,623)	8,436
Other changes in noncurrent assets and liabilities			9,297	(5,003)
Net cash provided by operating activities			8,636	7,529
Investing activities:
Utility plant expenditures			(3,227)	(3,984)
Investment in affiliates				0
Changes in affiliate advances			(319)	(82)
Reduction of affiliate short-term borrowings			0
Issuance of affiliate short-term borrowings			0
Reduction of affiliates long-term debt			0	0
Life insurance proceeds			0
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(3,546)	(4,066)
Financing Activities:
Short-term borrowings			0	0
Repayment of short-term borrowings			0	0
Debt issuance costs				0
Investment from affiliates			4,615	1,000
Changes in affiliate advances			(4,510)	(2,685)
Repayment of affiliate short-term borrowings			(2,000)
Repayment of affiliates long-term borrowings			(829)	(767)
Proceeds from long-term debt			0	50
Repayment of long-term debt			(349)	(398)
Advances and contributions in aid of construction			90	59
Refunds of advances for construction			(22)	(36)
Dividends paid to non-affiliates			(634)	0
Dividends paid to affiliates			0	(293)
Net cash provided by financing activities			(3,639)	(3,070)
Change in cash and cash equivalents			1,451	393
Cash and cash equivalents at beginning of period			3,985	1,550
Cash and cash equivalents at end of period	$ 5,436	$ 1,943	$ 5,436	$ 1,943