Contract Assets and Liabilities - Component of Contract Asset Balances (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Revenue From Contract With Customer [Abstract]
Costs in excess of billings and estimated earnings	$ 171,083	$ 120,223	$ 98,115
Contract retention	89,167	99,531	80,548
Total contract assets	$ 260,250	$ 219,754	$ 178,663

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(c))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 910
-SubTopic 310
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68065756&loc=d3e49370-109356

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