Business Segments - Schedule of PPE and Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Details of reportable segment
Total net property, plant and equipment (4)	$ 2,240,869	$ 2,099,625
Other assets	414,404	400,584
Total Assets	2,655,273	2,500,209
Reportable Legal Entities
Details of reportable segment
Total net property, plant and equipment (4)	2,240,869	2,099,625
Other assets	410,912	396,939
Total Assets	2,651,781	2,496,564
Intersegment Eliminations
Details of reportable segment
Total net property, plant and equipment (4)	0	0
Other assets	(1,129,192)	(1,042,087)
Total Assets	(1,129,192)	(1,042,087)
AWR | Intersegment Eliminations
Details of reportable segment
Total net property, plant and equipment (4)	0	0
Other assets	1,132,684	1,045,732
Total Assets	1,132,684	1,045,732
GOLDEN STATE WATER COMPANY
Details of reportable segment
Total net property, plant and equipment (4)	2,035,102	1,911,369
Total Assets	2,265,547	2,131,981
GOLDEN STATE WATER COMPANY | Reportable Legal Entities | Water:
Details of reportable segment
Total net property, plant and equipment (4)	2,035,102	1,911,369
Other assets	230,445	220,612
Total Assets	2,265,547	2,131,981
BVES | Reportable Legal Entities | Electric:
Details of reportable segment
Total net property, plant and equipment (4)	185,573	170,349
Other assets	57,516	50,048
Total Assets	243,089	220,397
ASUS | Reportable Legal Entities | Contracted services:
Details of reportable segment
Total net property, plant and equipment (4)	20,194	17,907
Other assets	122,951	126,279
Total Assets	$ 143,145	$ 144,186