Fair Value of Financial Instruments - Schedule of Outstanding Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair value of financial instruments
Unamortized Debt Issuance Expense	$ 3,400	$ 3,400
Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	580,264	450,373
Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	564,605	424,151
GOLDEN STATE WATER COMPANY
Fair value of financial instruments
Unamortized Debt Issuance Expense	3,200	3,200
GOLDEN STATE WATER COMPANY | Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	545,264	415,373
GOLDEN STATE WATER COMPANY | Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	$ 530,671	$ 391,198