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Revenue From Customers - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Costs and Estimated Earnings in Excess of Billings          
Disaggregation of Revenue [Line Items]          
Contracts receivable unpaid project contract price $ 14,300   $ 14,300   $ 7,142
Operating income (Loss)          
Disaggregation of Revenue [Line Items]          
Estimated construction gain (loss) before tax $ 3,727 $ 2,197 $ 12,032 $ 2,292