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Summary of Significant Accounting Policies (Revenue, Balancing and Memorandum Accounts) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Revenue from External Customer [Line Items] |  |  |
Regulated operating revenue, water surcharge | $ 5,235 | $ 3,807 | $ 4,605
San Jose Water Company [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Nonregulated operating revenue | $ 7,419 | $ 6,451 | $ 6,145

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- Definition Regulated Operating Revenue, Water Surcharge + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The amount of unregulated operating revenues recognized during the period. + References No definition available. + Details
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- Details
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