| **Financial Instruments (Narrative) (Details) - USD ($) $ in Thousands**          | Mar. 31, 2019 | Dec. 31, 2018 |
|-----------------------------------------------------------------------------------|---------------|---------------|
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]** |          |          |
| Cash and cash equivalents                                                         | $ 4,053       | $ 3,627       |
| Customers' advances for construction                                              | 99,186        | 93,343        |
| Fair Value, Inputs, Level 1 [Member]                                              |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]** |          |          |
| Loans payable                                                                     | 32,563        | 15,449        |
| Mutual funds                                                                      | 22,068        | 20,388        |
| Fair Value, Inputs, Level 2 [Member]                                              |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]** |          |          |
| Interest rate swap                                                                | 94,561        | 59,779        |
| Customers' advances for construction                                              | $ 99,186      | $ 93,343      |

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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as noncurrent.
+ References
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| - Definition
Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.
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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.
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| - Definition
Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.
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| - Definition
Fair value portion of contractual obligation to pay money on demand or on fixed or determinable dates.
+ References
No definition available.
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