Revenue Recognition - Contracts Receivable and Retainage (Details) - USD ($) $ in Thousands	3 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract receivable	$ 28,933	$ 28,466
Allowance for bad debt	3,700
Increase in allowance for bad debt	2,800
Contracts in progress	40,187	28,373
Advance billings on contracts	14,930	5,136
Accrued contract losses	6,033	$ 7,618
Contract Receivable \| Customer Concentration Risk \| One Major Customer
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract receivable	18,400
Costs in Excess of Billings \| Customer Concentration Risk \| Three Customers
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contracts in progress	37,100
Billings in Excess of Costs \| Customer Concentration Risk \| Five Customers
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer advances	$ 11,200

For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

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Amount of increase (decrease) in the allowance for doubtful accounts.

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- Definition

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 billed to customers under long-term contracts or programs to be collected in the next fiscal year following the latest fiscal year. Excludes amounts due that have been withheld because of retainage provisions in a contract. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

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.

+ References

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- Definition

Refundable consideration, usually cash, held by the entity pending satisfactory completion of the entity's obligations or pending the closing of a contract.

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-Publisher FASB
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-SubTopic 210
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Cumulative provision for contract losses not offset against related costs accumulated on the balance sheet.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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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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