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Fair Value of Financial Instruments: (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Golden State Water Company | Carrying Amount |  |
Financial liabilities: |  |
Long-term debt - GSWC | $ 324,978 | $ 325,265
Golden State Water Company | Fair Value |  |
Financial liabilities: |  |
Long-term debt - GSWC | 389,438 | $ 424,042
Mutual Funds | Fair Value, Inputs, Level 1 |  |
Financial liabilities: |  |
Rabbi trust fair value of investments held | $ 17,800 |

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