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Organization, Summary of Significant Accounting Policies and Recent Developments (Narrative) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Organization, Summary Of Significant Accounting Policies And Recent Developments [Line Items] |  |  |
Percent voting interest | 50.00% |  |
Percent of operating revenues | 88.00% |  |
Percent of total assets | 99.00% |  |
Allowance for doubtful accounts | $ 1,000 | $ 900 |
Bad debt expense | 800 | 500 | $ 700
Write-offs | 700 | 500 | 600
Investment | 200 |  |
Loan to RGRME | 1,700 |  |
Uncollectible notes receivable | 1,700 |  |
Noncash impairment charge | 200 |  |
Cash, Cash Equivalents and Restricted Cash, Beginning | 1,500 | 400 | 400
Cash, Cash Equivalents and Restricted Cash, Ending |  | 1,500 | 400
Operations and Maintenance expense and Other Income (Expense), net |  | $ 800 | $ 300
Effect of lease liability and right-of-use asset | $ 7,300 |  |
Minimum [Member] |  |  |
Organization, Summary Of Significant Accounting Policies And Recent Developments [Line Items] |  |  |
Estimated useful lives of non-regulated fixed assets | 3 years |  |
Maximum [Member] |  |  |
Organization, Summary Of Significant Accounting Policies And Recent Developments [Line Items] |  |  |
Estimated useful lives of non-regulated fixed assets | 40 years |  |

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