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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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