Contracts in Progress (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Contractors [Abstract]
Contract revenues	$ 165,985	$ 159,767	$ 309,090	$ 296,610
Costs incurred on uncompleted contracts	630,685		630,685		$ 461,144
Estimated earnings	112,786		112,786		73,170
Costs incurred and estimated earnings on uncompleted contracts	743,471		743,471		534,314
Less: Billings to date	(771,794)		(771,794)		(546,858)
Costs and estimated earnings in excess of billings on uncompleted contracts, net	(28,323)		(28,323)		(12,544)
Costs and estimated earnings in excess of billings on uncompleted contracts	23,641		23,641		9,217
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (51,964)		$ (51,964)		$ (21,761)

Costs in Excess of Billings on Uncompleted Contracts, Net

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Inventory for Long-term Contracts or Programs, Costs Incurred on Uncompleted Contracts

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Inventory for Long-term Contracts or Programs, Estimated Earnings on Uncompleted Contracts

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Amounts due for billed services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party. An example would be amounts billed to customers under contracts or programs but not paid as of the balance sheet date.

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Liability attributable to (i) billings in excess of costs under the percentage of completion contract accounting method representing the difference between contractually invoiced amounts (billings) and revenue recognized based, for example, on costs incurred to estimated total costs at period end or (ii) contractually invoiced amounts (billings) in excess of costs incurred and accumulated under the completed contract accounting method that are expected to be realized within one year or one operating cycle, whichever is longer, from the reporting date.

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Amount of receivable reflecting the cost incurred on uncompleted contracts in excess of related billings which is expected to be collected within one year or the normal operating cycle, if longer.

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Amount before valuation and LIFO reserves, and progress payments, of inventory associated with long-term contracts, expected to be sold, or consumed within one year or operating cycle, if longer.

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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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