Revenue Recognition - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Contracts with Customers, Asset and Liability [Line Items]
Advance billings on contracts	$ 67,066	$ 75,425
Unbilled receivables
Contracts with Customers, Asset and Liability [Line Items]
Contract with customer, asset	418,652	365,861
Retainages
Contracts with Customers, Asset and Liability [Line Items]
Contract with customer, asset	72,130	46,670
Retainages
Contracts with Customers, Asset and Liability [Line Items]
Contract with customer, asset	$ 1,447	$ 1,412

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130533-203044

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant