Revenues Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Operating revenues	$ 658,073	$ 595,459	$ 595,699
GSWC
Disaggregation of Revenue [Line Items]
Operating revenues	464,114	417,410	433,473
GSWC \| Water:
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	464,381	411,316	400,331
Operating revenues	464,114	417,410	433,473
GSWC \| Water: \| Tariff-based revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	456,156	405,756	394,623
GSWC \| Water: \| CPUC-approved surcharges (cost-recovery activities)
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	5,558	2,914	2,955
GSWC \| Water: \| Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	2,667	2,646	2,753
GSWC \| Water: \| Alternative revenue program
Disaggregation of Revenue [Line Items]
Under/(over)-collection (alternative revenue program)	(267)	6,094	33,142
BVES \| Electric:
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	55,075	50,801	40,697
Operating revenues	57,217	51,645	41,832
BVES \| Electric: \| Tariff-based revenues
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	51,063	50,628	40,130
BVES \| Electric: \| CPUC-approved surcharges (cost-recovery activities)
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	4,012	173	567
BVES \| Electric: \| Alternative revenue program
Disaggregation of Revenue [Line Items]
Under/(over)-collection (alternative revenue program)	2,142	844	1,135
American States Utility Services \| Contracted services:
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	136,742	126,404	120,394
American States Utility Services \| Contracted services: \| Water
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	74,305	72,951	75,785
American States Utility Services \| Contracted services: \| Wastewater
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	$ 62,437	$ 53,453	$ 44,609

AMERICAN STATES WATER CO 10-K