Concentration of Risk and Enterprise Wide Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Concentration Risk [Line Items]
Allowance for credit losses	$ (3,011)		$ (2,600)
Contract revenues	$ 166,620	$ 143,105
Foreign
Concentration Risk [Line Items]
Contract revenues, percent	2.40%	0.40%
Customer concentration risk \| Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 147,761		161,687
Allowance for credit losses	(3,011)		(2,600)
Trade and retainage receivables	$ 144,750		$ 159,087
Concentration risk, percentage	100.00%		100.00%
Customer concentration risk \| Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 166,620	$ 143,105
Contract revenues, percent	100.00%	100.00%
Customer concentration risk \| Federal Government \| Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 1,340		$ 4,765
Concentration risk, percentage	1.00%		3.00%
Customer concentration risk \| Federal Government \| Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 5,319	$ 10,277
Contract revenues, percent	3.00%	7.00%
Customer concentration risk \| State Governments \| Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 3,703		$ 5,864
Concentration risk, percentage	2.00%		4.00%
Customer concentration risk \| State Governments \| Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 12,232	$ 4,055
Contract revenues, percent	7.00%	3.00%
Customer concentration risk \| Local Governments \| Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 31,094		$ 41,944
Concentration risk, percentage	21.00%		26.00%
Customer concentration risk \| Local Governments \| Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 52,012	$ 44,430
Contract revenues, percent	31.00%	31.00%
Customer concentration risk \| Private Companies \| Trade and contract retainage receivables
Concentration Risk [Line Items]
Gross receivables	$ 111,624		$ 109,114
Concentration risk, percentage	76.00%		67.00%
Customer concentration risk \| Private Companies \| Trade and contract retainage receivables \| Two Customers [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	22.30%
Customer concentration risk \| Private Companies \| Contract revenues
Concentration Risk [Line Items]
Contract revenues	$ 97,057	$ 84,343
Contract revenues, percent	58.00%	59.00%

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Trade Accounts Receivable and Contract Receivable Retainage, Gross

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Trade Accounts Receivable and Contract Receivable Retainage, Net

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Amount of allowance for credit loss on accounts receivable, classified as current.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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