CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 2) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Utility plant:
Utility plant	$ 2,717,339	$ 2,506,946
Less accumulated depreciation and amortization	(858,062)	(805,178)
Net utility plant	1,859,277	1,701,768
Current assets:
Cash and cash equivalents	25,492	8,837	$ 19,587	$ 27,506
Receivables and unbilled revenue	103,023	104,505
Receivables from affiliates	0	0
Other current assets	13,554	14,236
Total current assets	142,069	127,578
Other assets:
Regulatory assets	355,930	361,893
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	54,469	50,014
Total other assets	410,399	411,907
TOTAL ASSETS	2,411,745	2,241,253
Capitalization:
Common stockholders' equity	659,471	642,155	626,626	598,756
Affiliate long-term debt	0	0
Long-term debt, less current maturities	531,745	508,002
Total capitalization	1,191,216	1,150,157
Current liabilities:
Current maturities of long-term debt	26,208	6,043
Short-term borrowings	97,100	33,615
Payables to affiliates	0	0
Accounts payable	77,813	66,380
Accrued expenses and other liabilities	49,109	41,860
Total current liabilities	250,230	147,898
Unamortized investment tax credits	1,798	1,872
Deferred income taxes	298,924	264,897
Pension and postretirement benefits other than pensions	222,691	236,266
Regulatory and other long-term liabilities	83,648	82,414
Advances for construction	182,448	180,172
Contributions in aid of construction	180,790	177,577
TOTAL CAPITALIZATION AND LIABILITIES	2,411,745	2,241,253
Consolidating Adjustments
Utility plant:
Utility plant	(7,197)	(7,197)
Less accumulated depreciation and amortization	1,919	1,823
Net utility plant	(5,278)	(5,374)
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables and unbilled revenue	0	0
Receivables from affiliates	(23,182)	(45,896)
Other current assets	0
Total current assets	(23,182)	(45,896)
Other assets:
Regulatory assets	0	0
Investments in affiliates	(666,525)	(651,449)
Long-term affiliate notes receivable	(25,744)	(25,099)
Other assets	(33)	(904)
Total other assets	(692,302)	(677,452)
TOTAL ASSETS	(720,762)	(728,722)
Capitalization:
Common stockholders' equity	(671,836)	(656,816)
Affiliate long-term debt	(25,744)	(25,099)
Long-term debt, less current maturities	0
Total capitalization	(697,580)	(681,915)
Current liabilities:
Current maturities of long-term debt	0	0
Short-term borrowings	0	0
Payables to affiliates	(23,182)	(45,896)
Accounts payable	0	0
Accrued expenses and other liabilities	0	0
Total current liabilities	(23,182)	(45,896)
Unamortized investment tax credits	0	0
Deferred income taxes	0	(911)
Pension and postretirement benefits other than pensions	0	0
Regulatory and other long-term liabilities	0	0
Advances for construction	0	0
Contributions in aid of construction	0	0
TOTAL CAPITALIZATION AND LIABILITIES	(720,762)	(728,722)
Parent Company
Utility plant:
Utility plant	1,318	1,318
Less accumulated depreciation and amortization	(826)	(605)
Net utility plant	492	713
Current assets:
Cash and cash equivalents	5,216	582	4,108	5,280
Receivables and unbilled revenue	0	0
Receivables from affiliates	19,566	19,677
Other current assets	80	79
Total current assets	24,862	20,338
Other assets:
Regulatory assets	0	0
Investments in affiliates	666,525	651,449
Long-term affiliate notes receivable	25,744	25,099
Other assets	376	758
Total other assets	692,645	677,306
TOTAL ASSETS	717,999	698,357
Capitalization:
Common stockholders' equity	659,471	642,155
Affiliate long-term debt	0	0
Long-term debt, less current maturities	0	0
Total capitalization	659,471	642,155
Current liabilities:
Current maturities of long-term debt	0	0
Short-term borrowings	57,100	33,615
Payables to affiliates	0	21,500
Accounts payable	0	0
Accrued expenses and other liabilities	88	102
Total current liabilities	57,188	55,217
Unamortized investment tax credits	0	0
Deferred income taxes	1,340	985
Pension and postretirement benefits other than pensions	0	0
Regulatory and other long-term liabilities	0	0
Advances for construction	0	0
Contributions in aid of construction	0	0
TOTAL CAPITALIZATION AND LIABILITIES	717,999	698,357
Cal Water
Utility plant:
Utility plant	2,519,785	2,313,704
Less accumulated depreciation and amortization	(805,992)	(758,362)
Net utility plant	1,713,793	1,555,342
Current assets:
Cash and cash equivalents	13,215	4,270	13,929	20,790
Receivables and unbilled revenue	98,850	100,777
Receivables from affiliates	3,608	26,219
Other current assets	12,442	13,077
Total current assets	128,115	144,343
Other assets:
Regulatory assets	352,139	358,254
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	50,361	45,544
Total other assets	402,500	403,798
TOTAL ASSETS	2,244,408	2,103,483
Capitalization:
Common stockholders' equity	595,003	581,792
Affiliate long-term debt	0	0
Long-term debt, less current maturities	530,850	507,034
Total capitalization	1,125,853	1,088,826
Current liabilities:
Current maturities of long-term debt	25,657	5,654
Short-term borrowings	40,000	0
Payables to affiliates	539	667
Accounts payable	74,998	63,814
Accrued expenses and other liabilities	47,232	40,173
Total current liabilities	188,426	110,308
Unamortized investment tax credits	1,798	1,872
Deferred income taxes	296,781	264,823
Pension and postretirement benefits other than pensions	222,691	236,266
Regulatory and other long-term liabilities	80,518	79,477
Advances for construction	181,907	179,630
Contributions in aid of construction	146,434	142,281
TOTAL CAPITALIZATION AND LIABILITIES	2,244,408	2,103,483
All Other Subsidiaries
Utility plant:
Utility plant	203,433	199,121
Less accumulated depreciation and amortization	(53,163)	(48,034)
Net utility plant	150,270	151,087
Current assets:
Cash and cash equivalents	7,061	3,985	$ 1,550	$ 1,436
Receivables and unbilled revenue	4,173	3,728
Receivables from affiliates	8	0
Other current assets	1,032	1,080
Total current assets	12,274	8,793
Other assets:
Regulatory assets	3,791	3,639
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	3,765	4,616
Total other assets	7,556	8,255
TOTAL ASSETS	170,100	168,135
Capitalization:
Common stockholders' equity	76,833	75,024
Affiliate long-term debt	25,744	25,099
Long-term debt, less current maturities	895	968
Total capitalization	103,472	101,091
Current liabilities:
Current maturities of long-term debt	551	389
Short-term borrowings	0	0
Payables to affiliates	22,643	23,729
Accounts payable	2,815	2,566
Accrued expenses and other liabilities	1,789	1,585
Total current liabilities	27,798	28,269
Unamortized investment tax credits	0	0
Deferred income taxes	803	0
Pension and postretirement benefits other than pensions	0	0
Regulatory and other long-term liabilities	3,130	2,937
Advances for construction	541	542
Contributions in aid of construction	34,356	35,296
TOTAL CAPITALIZATION AND LIABILITIES	$ 170,100	$ 168,135