Construction Contracts - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Contractors [Abstract]
Deferred precontract costs	$ 0.6	$ 1.5
Construction receivables retentions	9.9	11.5
Retention payable	$ 17.4	$ 14.6

Amount of deferred costs for long-term contracts and programs. Includes, but is not limited to, initial tooling costs and deferred production costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6)(d)(i))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Period Type:	instant

- Definition

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 910
-SubTopic 310
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68065756&loc=d3e49370-109356

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(c)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	debit
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- References

No definition available.

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- Definition

Amounts owed to vendors and subcontractors that have been withheld because of retainage provisions in a contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 910
-SubTopic 405
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68049106&loc=d3e50610-109371

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant