CONDENSED CONSOLIDATING FINANCIAL STATEMENTS (Details 3) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Consolidating Financial Statements
Operating revenue	$ 150,930	$ 184,268	$ 152,445	$ 121,727	$ 138,426	$ 183,543	$ 144,414	$ 121,985	$ 609,370	$ 588,368	$ 597,499
Operations:
Purchased water									181,515	168,557	177,884
Purchased power									27,180	27,890	33,159
Pump taxes									11,298	11,479	12,898
Administrative and general									98,474	113,110	97,373
Other									80,082	67,248	65,807
Maintenance									22,993	21,463	19,854
Depreciation and amortization									63,599	61,381	61,217
Income tax (benefit) expense									24,804	24,528	26,727
Property and other taxes									23,231	21,559	20,733
Total operating expenses									533,176	517,215	515,652
Net operating income	$ 21,335	$ 30,055	$ 18,534	$ 6,270	$ 14,962	$ 32,201	$ 16,493	$ 7,497	76,194	71,153	81,847
Other income and expenses:
Non-regulated revenue									16,585	15,624	17,318
Non-regulated expenses									(11,445)	(14,044)	(14,285)
(Loss) gain on sale of non-utility property									(146)	315	51
Income tax expense on other income and expenses									(2,012)	(761)	(1,245)
Net other income									2,982	1,134	1,839
Interest expense:
Interest expense									33,466	29,185	28,483
Less: capitalized interest									(2,965)	(1,915)	(1,535)
Net interest expense									30,501	27,270	26,948
Equity earnings of subsidiaries									0	0	0
Net income									48,675	45,017	56,738
Consolidating Adjustments
Condensed Consolidating Financial Statements
Operating revenue									0	0	0
Operations:
Purchased water									0	0	0
Purchased power									0	0	0
Pump taxes									0	0	0
Administrative and general									0	0	0
Other									(505)	(505)	(505)
Maintenance									0	0	0
Depreciation and amortization									(96)	(101)	(107)
Income tax (benefit) expense									1,010	1,008	964
Property and other taxes									0	0	0
Total operating expenses									409	402	352
Net operating income									(409)	(402)	(352)
Other income and expenses:
Non-regulated revenue									(2,385)	(2,322)	(2,170)
Non-regulated expenses									0	0	0
(Loss) gain on sale of non-utility property									0	0	0
Income tax expense on other income and expenses									972	967	920
Net other income									(1,413)	(1,355)	(1,250)
Interest expense:
Interest expense									(1,879)	(1,817)
Less: capitalized interest									0	0	0
Net interest expense									(1,879)	(1,817)	(1,666)
Equity earnings of subsidiaries									(48,158)	(44,516)	(56,064)
Net income									(48,101)	(44,456)	(56,000)
Parent Company
Condensed Consolidating Financial Statements
Operating revenue									0	0	0
Operations:
Purchased water									0	0	0
Purchased power									0	0	0
Pump taxes									0	0	0
Administrative and general									0	0	66
Other									0	0	0
Maintenance									0	0	0
Depreciation and amortization									220	228	214
Income tax (benefit) expense									(398)	(388)	(275)
Property and other taxes									0	0	0
Total operating expenses									(178)	(160)	5
Net operating income									178	160	(5)
Other income and expenses:
Non-regulated revenue									1,850	1,787	1,811
Non-regulated expenses									0	0	0
(Loss) gain on sale of non-utility property									0	0	0
Income tax expense on other income and expenses									(754)	(728)	(738)
Net other income									1,096	1,059	1,073
Interest expense:
Interest expense									757	718
Less: capitalized interest									0	0	0
Net interest expense									757	718	394
Equity earnings of subsidiaries									48,158	44,516	56,064
Net income									48,675	45,017	56,738
Cal Water
Condensed Consolidating Financial Statements
Operating revenue									570,514	552,202	564,508
Operations:
Purchased water									181,018	168,157	177,561
Purchased power									19,791	20,282	24,089
Pump taxes									11,298	11,479	12,898
Administrative and general									88,001	101,244	87,130
Other									73,918	61,154	59,291
Maintenance									22,053	20,659	19,141
Depreciation and amortization									59,138	56,911	56,836
Income tax (benefit) expense									22,743	23,964	27,286
Property and other taxes									20,331	18,848	18,086
Total operating expenses									498,291	482,698	482,318
Net operating income									72,223	69,504	82,190
Other income and expenses:
Non-regulated revenue									15,114	14,460	16,085
Non-regulated expenses									(10,122)	(12,870)	(13,086)
(Loss) gain on sale of non-utility property									(146)	315	51
Income tax expense on other income and expenses									(1,976)	(776)	(1,243)
Net other income									2,870	1,129	1,807
Interest expense:
Interest expense									32,682	28,450
Less: capitalized interest									(2,905)	(1,873)	(1,460)
Net interest expense									29,777	26,577	26,317
Equity earnings of subsidiaries									0	0	0
Net income									45,316	44,056	57,680
All Other Subsidiaries
Condensed Consolidating Financial Statements
Operating revenue									38,856	36,166	32,991
Operations:
Purchased water									497	400	323
Purchased power									7,389	7,608	9,070
Pump taxes									0	0	0
Administrative and general									10,473	11,866	10,177
Other									6,669	6,599	7,021
Maintenance									940	804	713
Depreciation and amortization									4,337	4,343	4,274
Income tax (benefit) expense									1,449	(56)	(1,248)
Property and other taxes									2,900	2,711	2,647
Total operating expenses									34,654	34,275	32,977
Net operating income									4,202	1,891	14
Other income and expenses:
Non-regulated revenue									2,006	1,699	1,592
Non-regulated expenses									(1,323)	(1,174)	(1,199)
(Loss) gain on sale of non-utility property									0	0	0
Income tax expense on other income and expenses									(254)	(224)	(184)
Net other income									429	301	209
Interest expense:
Interest expense									1,906	1,834
Less: capitalized interest									(60)	(42)	(75)
Net interest expense									1,846	1,792	1,903
Equity earnings of subsidiaries									0	0	0
Net income									$ 2,785	$ 400	$ (1,680)