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Costs and Estimated Earnings on Uncompleted Contracts (Narrative) (Details) - customer | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract] |  |
Costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings, percentage comprised by significant customers | 96.30% | 87.90%
Number of significant customers | 8 | 8

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