CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 2) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Utility plant:
Utility plant	$ 2,506,946	$ 2,342,471
Less accumulated depreciation and amortization	(805,178)	(752,040)
Net utility plant	1,701,768	1,590,431
Current assets:
Cash and cash equivalents	8,837	19,587	$ 27,506	$ 38,790
Receivables and unbilled revenue	104,505	116,878
Receivables from affiliates	0	0
Other current assets	14,236	17,659
Total current assets	127,578	154,124
Other assets:
Regulatory assets	361,893	390,331
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	54,856	52,465
Total other assets	416,749	442,796
ASSETS	2,246,095	2,187,351
Capitalization:
Common stockholders' equity	642,155	626,626	598,756	473,712
Affiliate long-term debt	0	0
Long-term debt, less current maturities	512,287	419,233
Total capitalization	1,154,442	1,045,859
Current liabilities:
Current maturities of long-term debt	6,600	6,607
Short-term borrowings	33,615	79,115
Payables to affiliates	0	0
Accounts payable	66,380	59,395
Accrued expenses and other liabilities	41,860	72,589
Total current liabilities	148,455	217,706
Unamortized investment tax credits	1,872	2,032
Deferred income taxes	264,897	214,842
Pension and postretirement benefits other than pension	236,266	270,865
Regulatory and other long-term liabilities	82,414	83,279
Advances for construction	180,172	182,284
Contributions in aid of construction	177,577	170,484
CAPITALIZATION AND LIABILITIES	2,246,095	2,187,351
Consolidating Adjustments
Utility plant:
Utility plant	(7,197)	(7,197)
Less accumulated depreciation and amortization	1,823	1,722
Net utility plant	(5,374)	(5,475)
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables and unbilled revenue	0	(1,051)
Receivables from affiliates	$ (45,896)	(23,609)
Other current assets		0
Total current assets	$ (45,896)	(24,660)
Other assets:
Regulatory assets	0	0
Investments in affiliates	(651,449)	(637,998)
Long-term affiliate notes receivable	(25,099)	(25,263)
Other assets	(904)	(321)
Total other assets	(677,452)	(663,582)
ASSETS	(728,722)	(693,717)
Capitalization:
Common stockholders' equity	(656,816)	(643,426)
Affiliate long-term debt	$ (25,099)	(25,263)
Long-term debt, less current maturities		0
Total capitalization	$ (681,915)	(668,689)
Current liabilities:
Current maturities of long-term debt	0	0
Short-term borrowings	0	0
Payables to affiliates	(45,896)	(23,609)
Accounts payable	0	(201)
Accrued expenses and other liabilities	0	(756)
Total current liabilities	(45,896)	(24,566)
Unamortized investment tax credits	0	0
Deferred income taxes	(911)	(462)
Pension and postretirement benefits other than pension	0	0
Regulatory and other long-term liabilities	0	0
Advances for construction	0	0
Contributions in aid of construction	0	0
CAPITALIZATION AND LIABILITIES	(728,722)	(693,717)
Parent Company
Utility plant:
Utility plant	1,318	1,318
Less accumulated depreciation and amortization	(605)	(377)
Net utility plant	713	941
Current assets:
Cash and cash equivalents	582	4,108	5,280	1,470
Receivables and unbilled revenue	0	0
Receivables from affiliates	19,677	20,001
Other current assets	79	0
Total current assets	20,338	24,109
Other assets:
Regulatory assets	0	0
Investments in affiliates	651,449	637,998
Long-term affiliate notes receivable	25,099	25,263
Other assets	758	891
Total other assets	677,306	664,152
ASSETS	698,357	689,202
Capitalization:
Common stockholders' equity	642,155	626,626
Affiliate long-term debt	0	0
Long-term debt, less current maturities	0	0
Total capitalization	642,155	626,626
Current liabilities:
Current maturities of long-term debt	0	0
Short-term borrowings	33,615	61,715
Payables to affiliates	21,500	0
Accounts payable	0	0
Accrued expenses and other liabilities	102	861
Total current liabilities	55,217	62,576
Unamortized investment tax credits	0	0
Deferred income taxes	985	0
Pension and postretirement benefits other than pension	0	0
Regulatory and other long-term liabilities	0	0
Advances for construction	0	0
Contributions in aid of construction	0	0
CAPITALIZATION AND LIABILITIES	698,357	689,202
Cal Water
Utility plant:
Utility plant	2,313,704	2,154,146
Less accumulated depreciation and amortization	(758,362)	(710,840)
Net utility plant	1,555,342	1,443,306
Current assets:
Cash and cash equivalents	4,270	13,929	20,790	34,609
Receivables and unbilled revenue	100,777	108,815
Receivables from affiliates	26,219	3,608
Other current assets	13,077	16,443
Total current assets	144,343	142,795
Other assets:
Regulatory assets	358,254	387,387
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	50,386	47,617
Total other assets	408,640	435,004
ASSETS	2,108,325	2,021,105
Capitalization:
Common stockholders' equity	581,792	569,319
Affiliate long-term debt	0	0
Long-term debt, less current maturities	511,319	417,884
Total capitalization	1,093,111	987,203
Current liabilities:
Current maturities of long-term debt	6,211	6,173
Short-term borrowings	0	17,400
Payables to affiliates	667	270
Accounts payable	63,814	56,666
Accrued expenses and other liabilities	40,173	71,203
Total current liabilities	110,865	151,712
Unamortized investment tax credits	1,872	2,032
Deferred income taxes	264,823	210,789
Pension and postretirement benefits other than pension	236,266	270,865
Regulatory and other long-term liabilities	79,477	74,282
Advances for construction	179,630	181,763
Contributions in aid of construction	142,281	142,459
CAPITALIZATION AND LIABILITIES	2,108,325	2,021,105
All Other Subsidiaries
Utility plant:
Utility plant	199,121	194,204
Less accumulated depreciation and amortization	(48,034)	(42,545)
Net utility plant	151,087	151,659
Current assets:
Cash and cash equivalents	3,985	1,550	$ 1,436	$ 2,711
Receivables and unbilled revenue	3,728	9,114
Receivables from affiliates	0	0
Other current assets	1,080	1,216
Total current assets	8,793	11,880
Other assets:
Regulatory assets	3,639	2,944
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	4,616	4,278
Total other assets	8,255	7,222
ASSETS	168,135	170,761
Capitalization:
Common stockholders' equity	75,024	74,107
Affiliate long-term debt	25,099	25,263
Long-term debt, less current maturities	968	1,349
Total capitalization	101,091	100,719
Current liabilities:
Current maturities of long-term debt	389	434
Short-term borrowings	0	0
Payables to affiliates	23,729	23,339
Accounts payable	2,566	2,930
Accrued expenses and other liabilities	1,585	1,281
Total current liabilities	28,269	27,984
Unamortized investment tax credits	0	0
Deferred income taxes	0	4,515
Pension and postretirement benefits other than pension	0	0
Regulatory and other long-term liabilities	2,937	8,997
Advances for construction	542	521
Contributions in aid of construction	35,296	28,025
CAPITALIZATION AND LIABILITIES	$ 168,135	$ 170,761