Business Segments - Schedule of Reconciling Property Plant and Equipment to Consolidated Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	$ 2,099,625	$ 1,892,280
Other assets	400,584	353,842
Total Assets	2,500,209	2,246,122
AWR
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets	1,045,732	922,901
GSWC
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	1,911,369	1,735,534
Total Assets	2,131,981	1,916,155
Reportable Legal Entities
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	2,099,625	1,892,280
Other assets	396,939	349,725
Total Assets	2,496,564	2,242,005
Reportable Legal Entities | Water | GSWC
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	1,911,369	1,735,534
Other assets	220,612	180,621
Total Assets	2,131,981	1,916,155
Reportable Legal Entities | Electric | BVES
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	170,349	140,279
Other assets	50,048	35,241
Total Assets	220,397	175,520
Reportable Legal Entities | Contracted services: | American States Utility Services
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	17,907	16,467
Other assets	126,279	133,863
Total Assets	144,186	150,330
Intersegment Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	0	0
Other assets	(1,042,087)	(918,784)
Total Assets	(1,042,087)	(918,784)
Intersegment Eliminations | AWR
Segment Reporting, Asset Reconciling Item [Line Items]
Total utility plant	0	0
Other assets	1,045,732	922,901
Total Assets	$ 1,045,732	$ 922,901