Fair Value of Financial Instruments - Schedule of Outstanding Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair value of financial instruments
Unamortized Debt Issuance Expense	$ 3,300	$ 3,400
Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	580,122	450,373
Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	552,374	424,151
GOLDEN STATE WATER COMPANY
Fair value of financial instruments
Unamortized Debt Issuance Expense	3,100	3,200
GOLDEN STATE WATER COMPANY | Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	545,122	415,373
GOLDEN STATE WATER COMPANY | Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	$ 519,412	$ 391,198