Fair Value of Financial Instruments - Schedule of Outstanding Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Fair value of financial instruments
Unamortized debt issuance expense	$ 3,100	$ 3,400
Carrying Amount
Fair value of financial instruments
Long-term debt, fair value	794,025	794,310
Fair Value
Fair value of financial instruments
Long-term debt, fair value	775,757	790,820
GOLDEN STATE WATER COMPANY
Fair value of financial instruments
Unamortized debt issuance expense	2,700	3,000
GOLDEN STATE WATER COMPANY \| Carrying Amount
Fair value of financial instruments
Long-term debt, fair value	709,025	709,310
GOLDEN STATE WATER COMPANY \| Fair Value
Fair value of financial instruments
Long-term debt, fair value	$ 690,391	$ 703,319

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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+ Details