Fair Value of Financial Instruments - Schedule of Outstanding Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair value of financial instruments
Unamortized Debt Issuance Expense	$ 3,400	$ 3,100
Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	643,791	579,047
Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	603,019	556,214
GOLDEN STATE WATER COMPANY
Fair value of financial instruments
Unamortized Debt Issuance Expense	3,200	3,000
GOLDEN STATE WATER COMPANY | Reported Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	608,791	544,047
GOLDEN STATE WATER COMPANY | Estimate of Fair Value Measurement
Fair value of financial instruments
Long-term Debt, Fair Value	$ 570,888	$ 522,883