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Basis of Presentation and Significant Accounting Policies - Narrative (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Jun. 30, 2020
Financing Receivable, Impaired [Line Items] |  |  |
Increase in accounts receivable | $ 8,552,000 |  |
Allowance for credit loss | 0 | $ 0 |
Contract asset retainage | 44,412,000 | 52,124,000 |
Contract liability retainage | 33,856,000 | 27,251,000 |
Decrease in contract asset retainage | 9,704,000 |  |
Increase in contract liability retainage | 56,259,000 |  |
Contract liability recognized during the period | $ 444,213,000 |  |
Contract liability revenue recognized |  | 274,341,000 |
Retainage rate | 68.00% |  |
Consolidated ownership percentage | 50.00% |  | 50.00%
Other Current Assets |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Restricted cash | $ 6,500,000 | $ 4,800,000 |
Building and improvements | Minimum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Property, plant and equipment, useful life | 5 years |  |
Building and improvements | Maximum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Property, plant and equipment, useful life | 39 years |  |
Plant and field equipment | Minimum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Property, plant and equipment, useful life | 5 years |  |
Plant and field equipment | Maximum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Property, plant and equipment, useful life | 20 years |  |
Heavy Civil Construction | Minimum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 12 months |  |
Heavy Civil Construction | Maximum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 36 months |  |
Specialty Service | Minimum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 6 months |  |
Specialty Service | Maximum |  |  |
Financing Receivable, Impaired [Line Items] |  |  |
Revenue recognition, percentage of completion range | 24 months |  |

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