Contract Assets and Liabilities - Components of Contract Liabilities Balance (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Revenue From Contract With Customer [Abstract]
Billings in excess of costs and estimated earnings, net of retention	$ 117,029	$ 103,250	$ 91,147
Provisions for losses	2,260	2,199	717
Total contract liabilities	$ 119,289	$ 105,449	$ 91,864

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
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-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant