FINANCIAL STATEMENT SCHEDULE - Condensed Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Condensed Financial Statements, Captions [Line Items]
Operating revenue	$ 800,590	$ 748,439	$ 670,363
Operating expense:
Administrative and general	125,998	105,830	98,656
Property taxes and other non-income taxes	37,686	35,928	34,475
Total operating expense	623,063	577,936	520,928
Operating income	177,527	170,503	149,435
Other (expense) income:
Interest on long-term debt and other interest expense	(72,575)	(71,390)	(66,144)
Other, net	3,545	55	8,882
Income tax benefit	12,355	8,970	5,956
Net income	102,578	93,967	84,987
Other comprehensive income, net	(493)	169	314
Comprehensive income	102,085	94,136	85,301
H2O America
Condensed Financial Statements, Captions [Line Items]
Operating revenue	0	0	0
Operating expense:
Administrative and general	4,664	5,568	2,239
Property taxes and other non-income taxes	118	388	80
Total operating expense	4,782	5,956	2,319
Operating income	(4,782)	(5,956)	(2,319)
Other (expense) income:
Interest on long-term debt and other interest expense	(17,862)	(18,022)	(17,692)
Interest income on intercompany notes receivable	6,292	6,756	3,862
Other, net	(4,613)	(3,456)	1,034
Loss before income taxes and equity earnings from subsidiaries	(20,965)	(20,678)	(15,115)
Income tax benefit	(6,015)	(5,727)	(4,294)
Equity earnings from subsidiaries, net of taxes	117,528	108,918	95,808
Net income	$ 102,578	$ 93,967	$ 84,987