Business Segments: (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Details of reportable segment
Total operating revenues	$ 121,278	$ 124,647	$ 230,355	$ 226,380
Operating income (loss)	35,716	39,430	61,415	59,625
Interest expense, net	4,832	5,406	10,324	10,781
Utility plant	1,456,398	1,355,663	1,456,398	1,355,663	$ 1,415,705
Depreciation and amortization expense	9,031	6,655	17,842	17,487
Income tax expense (benefit)	8,281	7,831	12,182	11,141
Capital additions	29,043	40,593	$ 62,587	81,155
AWR
Details of reportable segment
Number of reportable segments | segment			3
GOLDEN STATE WATER COMPANY
Details of reportable segment
Public Utilities Property Plant and Equipment Depreciation on Transportation Equipment	83	96	$ 165	154
Number of reportable segments | segment			2
Total operating revenues	94,753	95,548	$ 177,145	170,900
Operating income (loss)	30,175	34,037	52,267	49,364
Utility plant	1,434,014		1,434,014		$ 1,394,742
Depreciation and amortization expense	8,209	6,006	16,238	15,995
Income tax expense (benefit)	7,309	6,826	10,537	8,946
GOLDEN STATE WATER COMPANY | Water Service Utility Operations
Details of reportable segment
Total operating revenues	87,074	88,140	158,498	152,863
GOLDEN STATE WATER COMPANY | Electric Service Utility Operations
Details of reportable segment
Total operating revenues	7,679	7,408	$ 18,647	18,037
ASUS | Contracted Services
Details of reportable segment
Period of fixed price contracts to operate and maintain water systems at various military bases			50 years
Reportable Legal Entities | GOLDEN STATE WATER COMPANY | Water Service Utility Operations
Details of reportable segment
Total operating revenues	87,074	88,140	$ 158,498	152,863
Operating income (loss)	28,662	33,259	47,267	46,525
Interest expense, net	4,857	5,112	9,990	10,349
Utility plant	1,353,671	1,273,962	1,353,671	1,273,962
Depreciation and amortization expense	7,601	5,405	15,023	14,794
Income tax expense (benefit)	6,970	6,812	9,348	8,485
Capital additions	22,076	36,293	50,535	74,672
Reportable Legal Entities | GOLDEN STATE WATER COMPANY | Electric Service Utility Operations
Details of reportable segment
Total operating revenues	7,679	7,408	18,647	18,037
Operating income (loss)	1,513	778	5,000	2,839
Interest expense, net	139	346	465	699
Utility plant	80,343	63,462	80,343	63,462
Depreciation and amortization expense	608	601	1,215	1,201
Income tax expense (benefit)	339	14	1,189	461
Capital additions	5,500	1,254	9,054	1,988
Reportable Legal Entities | ASUS | Contracted Services
Details of reportable segment
Total operating revenues	26,525	29,099	53,210	55,480
Operating income (loss)	5,543	5,395	9,152	10,265
Interest expense, net	(220)	219	(297)	580
Utility plant	22,384	18,239	22,384	18,239
Depreciation and amortization expense	822	649	1,604	1,492
Income tax expense (benefit)	1,301	1,300	2,049	2,425
Capital additions	1,467	3,046	2,998	4,495
Intersegment Eliminations | AWR
Details of reportable segment
Total operating revenues	0	0	0	0
Operating income (loss)	(2)	(2)	(4)	(4)
Interest expense, net	56	(167)	166	(313)
Utility plant	0	0	0	0
Depreciation and amortization expense	0	0		0
Income tax expense (benefit)	(329)	(295)	(404)	(230)
Capital additions	$ 0	$ 0		$ 0