Revenue from Contract with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
BRRAM under (over)-collection (alternative revenue program)	$ (7,679)	$ (7,408)	$ (18,647)	$ (18,037)
Total operating revenues	121,278	124,647	230,355	226,380
GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
BRRAM under (over)-collection (alternative revenue program)	(7,679)	(7,408)	(18,647)	(18,037)
Total operating revenues	94,753	95,548	177,145	170,900
Water Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	78,717	78,100	149,200	138,425
Regulated Operating Revenue	8,357	10,040	9,298	14,438
Total operating revenues	87,074	88,140	158,498	152,863
Electric Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	7,562	7,741	17,852	19,061
BRRAM under (over)-collection (alternative revenue program)	(117)	(333)	(795)	(1,024)
Total operating revenues	7,679	7,408	18,647	18,037
Contracted Services | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	26,525	29,099	53,210	55,480
Tariff-based Revenues | Water Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	77,264	76,876	146,518	136,451
Tariff-based Revenues | Electric Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	7,384	7,698	17,416	18,964
Surcharges (Cost-recovery Activities) | Water Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	962	763	1,696	1,054
Surcharges (Cost-recovery Activities) | Electric Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	178	43	436	97
Other Products and Services | Water Service Utility Operations | GOLDEN STATE WATER COMPANY
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	491	461	986	920
Water | Contracted Services | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	13,472	14,620	28,173	27,975
Wastewater | Contracted Services | ASUS
Disaggregation of Revenue [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 13,053	$ 14,479	$ 25,037	$ 27,505