Construction Contract and Other Service Revenues (Details) - Construction Contract Revenue - USD ($) $ in Thousands  | 
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019  | 
Jun. 30, 2018  | 
Jun. 30, 2019  | 
Jun. 30, 2018  | 
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| Disaggregation of Revenue [Line Items] | ||||
| Performance obligations satisfied or already satisfied | $ (14) | $ 10 | $ 18 | $ 319 | 
| Remaining performance obligations | 48,400 | 48,400 | ||
| Remaining performance obligation expected to be recognized during the remainder of year | $ 41,000 | $ 41,000 | ||
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- Definition Revenue, Remaining Performance Obligation, Amount to be Recognized During the Remainder of the Year No definition available. 
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- Definition Amount of revenue recognized from performance obligation satisfied or partially satisfied in previous reporting periods. Includes, but is not limited to, change in transaction price. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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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. No definition available. 
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- Definition Amount of transaction price allocated to performance obligation that has not been recognized as revenue. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Details 
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