Costs and Estimated Earnings and Billings on Uncompleted Contracts - Net Amount of Costs and Estimated Earning on Uncompleted Contracts Above (Below) Billings (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Contractors [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 37,112	$ 32,705
Billings in excess of costs and estimated earnings on uncompleted contracts	(62,374)	(64,100)
Net amount of costs and estimated earnings on uncompleted contracts below billings	$ (25,262)	$ (31,395)

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57788-111642

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57807-111642

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57795-111642

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Balance Type:	credit
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