CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Utility plant:
Utility plant	$ 3,229,446	$ 2,970,179
Less accumulated depreciation and amortization	(996,723)	(922,214)
Net utility plant	2,232,723	2,047,965
Current assets:
Cash and cash equivalents	47,176	94,776
Receivables and unbilled revenue	122,959	115,454
Receivables from affiliates	0	0
Other current assets	18,567	17,643
Total current assets	188,702	227,873
Other assets:
Regulatory assets	353,569	405,482
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	62,710	63,390
Total other assets	416,279	468,872
TOTAL ASSETS	2,837,704	2,744,710
Capitalization:
Common stockholders' equity	730,157	699,221	$ 659,471	$ 642,155
Affiliate long-term debt	0	0
Long-term debt, net	710,027	515,793
Total capitalization	1,440,184	1,215,014
Current liabilities:
Current maturities of long-term debt, net	104,911	15,920
Short-term borrowings	65,100	275,100
Payables to affiliates	0	0
Accounts payable	95,580	93,955
Accrued expenses and other liabilities	55,575	105,984
Total current liabilities	321,166	490,959
Unamortized investment tax credits	1,649	1,724
Deferred income taxes	213,033	194,617
Pension and postretirement benefits other than pensions	193,538	252,141
Regulatory and other long-term liabilities	256,522	221,032
Advances for construction	186,342	182,502
Contributions in aid of construction	225,270	186,721
TOTAL CAPITALIZATION AND LIABILITIES	2,837,704	2,744,710
Consolidating Adjustments
Utility plant:
Utility plant	(7,197)	(7,196)
Less accumulated depreciation and amortization	2,097	2,010
Net utility plant	(5,100)	(5,186)
Current assets:
Cash and cash equivalents	0	0
Receivables and unbilled revenue	0	0
Receivables from affiliates	(25,453)	(24,088)
Other current assets	0	0
Total current assets	(25,453)	(24,088)
Other assets:
Regulatory assets	0	0
Investments in affiliates	(733,156)	(698,690)
Long-term affiliate notes receivable	(27,829)	(26,441)
Other assets	(203)	(205)
Total other assets	(761,188)	(725,336)
TOTAL ASSETS	(791,741)	(754,610)
Capitalization:
Common stockholders' equity	(738,433)	(703,947)
Affiliate long-term debt	(27,828)	(26,441)
Long-term debt, net	0	0
Total capitalization	(766,261)	(730,388)
Current liabilities:
Current maturities of long-term debt, net	0	0
Short-term borrowings	0	0
Payables to affiliates	(25,453)	(24,088)
Accounts payable	0	0
Accrued expenses and other liabilities	0	0
Total current liabilities	(25,453)	(24,088)
Unamortized investment tax credits	0	0
Deferred income taxes	(43)	(134)
Pension and postretirement benefits other than pensions	0	0
Regulatory and other long-term liabilities	16	0
Advances for construction	0	0
Contributions in aid of construction	0	0
TOTAL CAPITALIZATION AND LIABILITIES	(791,741)	(754,610)
Parent Company | Reportable Legal Entities
Utility plant:
Utility plant	1,318	1,321
Less accumulated depreciation and amortization	(1,013)	(919)
Net utility plant	305	402
Current assets:
Cash and cash equivalents	3,779	4,728
Receivables and unbilled revenue	126	0
Receivables from affiliates	21,318	19,952
Other current assets	80	80
Total current assets	25,303	24,760
Other assets:
Regulatory assets	0	0
Investments in affiliates	733,156	698,690
Long-term affiliate notes receivable	27,829	26,441
Other assets	133	192
Total other assets	761,118	725,323
TOTAL ASSETS	786,726	750,485
Capitalization:
Common stockholders' equity	730,157	693,462
Affiliate long-term debt	0	0
Long-term debt, net	0	0
Total capitalization	730,157	693,462
Current liabilities:
Current maturities of long-term debt, net	0	0
Short-term borrowings	55,100	55,100
Payables to affiliates	17	0
Accounts payable	0	0
Accrued expenses and other liabilities	107	271
Total current liabilities	55,224	55,371
Unamortized investment tax credits	0	0
Deferred income taxes	1,376	1,652
Pension and postretirement benefits other than pensions	0	0
Regulatory and other long-term liabilities	(31)	0
Advances for construction	0	0
Contributions in aid of construction	0	0
TOTAL CAPITALIZATION AND LIABILITIES	786,726	750,485
Cal Water | Reportable Legal Entities
Utility plant:
Utility plant	3,021,437	2,771,259
Less accumulated depreciation and amortization	(938,072)	(868,762)
Net utility plant	2,083,365	1,902,497
Current assets:
Cash and cash equivalents	33,763	80,940
Receivables and unbilled revenue	118,632	110,928
Receivables from affiliates	4,074	4,093
Other current assets	16,907	16,569
Total current assets	173,376	212,530
Other assets:
Regulatory assets	349,414	401,668
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	58,959	59,581
Total other assets	408,373	461,249
TOTAL ASSETS	2,665,114	2,576,276
Capitalization:
Common stockholders' equity	659,340	632,059
Affiliate long-term debt	0	0
Long-term debt, net	709,444	514,952
Total capitalization	1,368,784	1,147,011
Current liabilities:
Current maturities of long-term debt, net	104,664	15,598
Short-term borrowings	10,000	220,000
Payables to affiliates	488	580
Accounts payable	92,310	90,561
Accrued expenses and other liabilities	53,655	104,002
Total current liabilities	261,117	430,741
Unamortized investment tax credits	1,649	1,724
Deferred income taxes	210,052	190,675
Pension and postretirement benefits other than pensions	193,538	252,141
Regulatory and other long-term liabilities	250,720	217,684
Advances for construction	185,843	181,979
Contributions in aid of construction	193,411	154,321
TOTAL CAPITALIZATION AND LIABILITIES	2,665,114	2,576,276
All Other Subsidiaries | Reportable Legal Entities
Utility plant:
Utility plant	213,888	204,795
Less accumulated depreciation and amortization	(59,735)	(54,543)
Net utility plant	154,153	150,252
Current assets:
Cash and cash equivalents	9,634	9,108
Receivables and unbilled revenue	4,201	4,526
Receivables from affiliates	61	43
Other current assets	1,580	994
Total current assets	15,476	14,671
Other assets:
Regulatory assets	4,155	3,814
Investments in affiliates	0	0
Long-term affiliate notes receivable	0	0
Other assets	3,821	3,822
Total other assets	7,976	7,636
TOTAL ASSETS	177,605	172,559
Capitalization:
Common stockholders' equity	79,093	77,647
Affiliate long-term debt	27,828	26,441
Long-term debt, net	583	841
Total capitalization	107,504	104,929
Current liabilities:
Current maturities of long-term debt, net	247	322
Short-term borrowings	0	0
Payables to affiliates	24,948	23,508
Accounts payable	3,270	3,394
Accrued expenses and other liabilities	1,813	1,711
Total current liabilities	30,278	28,935
Unamortized investment tax credits	0	0
Deferred income taxes	1,648	2,424
Pension and postretirement benefits other than pensions	0	0
Regulatory and other long-term liabilities	5,817	3,348
Advances for construction	499	523
Contributions in aid of construction	31,859	32,400
TOTAL CAPITALIZATION AND LIABILITIES	$ 177,605	$ 172,559