Condensed Consolidating Financial Statements (Details 4) - USD ($)	3 Months Ended		6 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2014
Operating activities:
Net income	$ 11,508,000	$ 9,845,000	$ 10,710,000	$ 11,420,000
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			32,701,000	31,652,000
Change in value of life insurance contracts			(336,000)	50,000
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			(221,000)	(3,403,000)
Other changes in noncurrent assets and liabilities			16,209,000	8,630,000
Net cash provided by operating activities			59,063,000	48,349,000
Investing activities:
Utility plant expenditures			(116,155,000)	(75,827,000)
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			495,000	0
Purchase of life insurance contracts			(1,065,000)	(214,000)
Change in restricted cash			(653,000)	46,000
Net cash used in investing activities			(117,378,000)	(75,995,000)
Financing Activities:
Short-term borrowings			103,100,000	52,500,000
Repayment of short-term borrowings			(61,615,000)	(5,000,000)
Debt issuance costs			(177,000)	0
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			49,823,000	50,000
Repayment of long-term debt			(2,463,000)	(2,554,000)
Advances and contributions in aid of construction			11,463,000	6,921,000
Refunds of advances for construction			(3,472,000)	(3,316,000)
Dividends paid to non-affiliates			(16,532,000)	(16,027,000)
Dividends paid to affiliates			0	0
Net cash provided by financing activities			80,304,000	32,574,000
Change in cash and cash equivalents			21,989,000	4,928,000
Cash and cash equivalents at beginning of period			8,837,000	19,587,000
Cash and cash equivalents at end of period	30,826,000	24,515,000	30,826,000	24,515,000
Consolidating Adjustments
Operating activities:
Net income	(11,357,000)	(9,736,000)	(10,406,000)	(11,126,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	11,371,000	9,751,000	10,434,000	11,156,000
Dividends received from affiliates			(16,532,000)	(16,027,000)
Depreciation and amortization			(48,000)	(51,000)
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			0	(94,000)
Other changes in noncurrent assets and liabilities			20,000	115,000
Net cash provided by operating activities			(16,532,000)	(16,027,000)
Investing activities:
Utility plant expenditures			0	0
Investment in affiliates				1,000,000
Changes in affiliate advances			(27,000)	1,467,000
Reduction of affiliate short-term borrowings			(44,100,000)
Issuance of affiliate short-term borrowings			23,215,000
Reduction of affiliates long-term debt			(544,000)	(517,000)
Life insurance proceeds			0
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(21,456,000)	1,950,000
Financing Activities:
Short-term borrowings			0	0
Repayment of short-term borrowings			0	0
Investment from affiliates			(23,215,000)	(1,000,000)
Changes in affiliate advances			27,000	(1,467,000)
Repayment of affiliate short-term borrowings			44,100,000
Repayment of affiliates long-term borrowings			544,000	517,000
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			16,532,000	16,027,000
Net cash provided by financing activities			37,988,000	14,077,000
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	11,508,000	9,845,000	10,710,000	11,420,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Equity earnings of subsidiaries	(11,371,000)	(9,751,000)	(10,434,000)	(11,156,000)
Dividends received from affiliates			16,532,000	16,027,000
Depreciation and amortization			114,000	114,000
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			(218,000)	(1,049,000)
Other changes in noncurrent assets and liabilities			892,000	1,897,000
Net cash provided by operating activities			17,596,000	17,253,000
Investing activities:
Utility plant expenditures			0	0
Investment in affiliates				(1,000,000)
Changes in affiliate advances			(561,000)	(4,234,000)
Reduction of affiliate short-term borrowings			2,000,000
Issuance of affiliate short-term borrowings			(2,615,000)
Reduction of affiliates long-term debt			544,000	517,000
Life insurance proceeds			0
Purchase of life insurance contracts			0	0
Change in restricted cash			0	0
Net cash used in investing activities			(632,000)	(4,717,000)
Financing Activities:
Short-term borrowings			42,100,000	2,500,000
Repayment of short-term borrowings			(20,615,000)	0
Investment from affiliates			20,600,000	0
Changes in affiliate advances			0	102,000
Repayment of affiliate short-term borrowings			(42,100,000)
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	(16,027,000)
Dividends paid to affiliates			(16,532,000)		$ 0
Net cash provided by financing activities			(16,547,000)	(13,425,000)
Change in cash and cash equivalents			417,000	(889,000)
Cash and cash equivalents at beginning of period			582,000	4,108,000
Cash and cash equivalents at end of period	999,000	3,219,000	999,000	3,219,000
Cal Water
Operating activities:
Net income	10,428,000	9,556,000	9,539,000	11,586,000
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			30,372,000	29,170,000
Change in value of life insurance contracts			(336,000)	50,000
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			(987,000)	(9,161,000)
Other changes in noncurrent assets and liabilities			14,567,000	12,057,000
Net cash provided by operating activities			53,155,000	43,702,000
Investing activities:
Utility plant expenditures			(113,894,000)	(72,872,000)
Investment in affiliates				0
Changes in affiliate advances			787,000	2,885,000
Reduction of affiliate short-term borrowings			42,100,000
Issuance of affiliate short-term borrowings			(20,600,000)
Reduction of affiliates long-term debt			0	0
Life insurance proceeds			495,000
Purchase of life insurance contracts			(1,065,000)	(214,000)
Change in restricted cash			(653,000)	46,000
Net cash used in investing activities			(92,830,000)	(70,155,000)
Financing Activities:
Short-term borrowings			61,000,000	50,000,000
Repayment of short-term borrowings			(41,000,000)	(5,000,000)
Investment from affiliates			0	0
Changes in affiliate advances			651,000	2,077,000
Repayment of affiliate short-term borrowings			0
Repayment of affiliates long-term borrowings			0		$ 0
Proceeds from long-term debt			49,823,000	0
Repayment of long-term debt			(2,287,000)	(2,310,000)
Advances and contributions in aid of construction			11,413,000	6,881,000
Refunds of advances for construction			(3,454,000)	(3,284,000)
Dividends paid to non-affiliates			(16,135,000)	0
Dividends paid to affiliates			0	(15,867,000)
Net cash provided by financing activities			60,011,000	32,497,000
Change in cash and cash equivalents			20,336,000	6,044,000
Cash and cash equivalents at beginning of period			4,270,000	13,929,000
Cash and cash equivalents at end of period	24,606,000	19,973,000	24,606,000	19,973,000
All Other Subsidiaries
Operating activities:
Net income	929,000	180,000	867,000	(460,000)
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			2,263,000	2,419,000
Change in value of life insurance contracts			0	0
Changes in operating assets and liabilities:
Changes in operating assets and liabilities:			984,000	6,901,000
Other changes in noncurrent assets and liabilities			730,000	(5,439,000)
Net cash provided by operating activities			4,844,000	3,421,000
Investing activities:
Utility plant expenditures			(2,261,000)	(2,955,000)
Investment in affiliates				0
Changes in affiliate advances			(199,000)	(118,000)
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			(2,460,000)	(3,073,000)
Financing Activities:
Short-term borrowings			0	0
Repayment of short-term borrowings			0	0
Investment from affiliates			2,615,000	1,000,000
Changes in affiliate advances			(678,000)	(712,000)
Repayment of affiliate short-term borrowings			(2,000,000)
Repayment of affiliates long-term borrowings			(544,000)	(517,000)
Proceeds from long-term debt			0	50,000
Repayment of long-term debt			(176,000)	(244,000)
Advances and contributions in aid of construction			50,000	40,000
Refunds of advances for construction			(18,000)	(32,000)
Dividends paid to non-affiliates			(397,000)	0
Dividends paid to affiliates			0	(160,000)
Net cash provided by financing activities			(1,148,000)	(575,000)
Change in cash and cash equivalents			1,236,000	(227,000)
Cash and cash equivalents at beginning of period			3,985,000	1,550,000
Cash and cash equivalents at end of period	$ 5,221,000	$ 1,323,000	$ 5,221,000	$ 1,323,000