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California Water Service Group Stock (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract] |  |  |  |
Available for Sale Marketable Security, Shares Sold | 82,340 |  | 100,000 |
Proceeds from Sale of Debt Securities, Available-for-sale | $ 3,398 |  | $ 4,112 |
Fees Incurred on Sale of Available for Sale Securities | 7 |  | 9 |
Available-for-sale Securities, Gross Realized Gain (Loss) | 191 | $ 0 | 104 | $ 0
Available for Sales Securities, Tax on Realized Gain | 53 |  | 29 |
Debt and Equity Securities, Gain (Loss) | $ 138 |  | $ 75 |
Available for Sale Marketable Security, Shares Held | 0 |  | 0 |

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