Quarterly report pursuant to Section 13 or 15(d)

Revenue Recognition on Construction Contract and Other Service Revenues (Details)

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Revenue Recognition on Construction Contract and Other Service Revenues (Details) - Construction Contract Revenue
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
USD ($)
compensation_arrangement
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
compensation_arrangement
Jun. 30, 2017
USD ($)
Disaggregation of Revenue [Line Items]        
Number of compensation arrangement types | compensation_arrangement 3   3  
Performance obligations satisfied or already satisfied $ 10 $ 401 $ 319 $ 547
Customers payment period     30 days  
Remaining performance obligations $ 16,100   $ 16,100