Revenue Recognition - Schedule of Cost and Estimated Earnings on Uncompleted Contracts (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Contractors [Abstract]
Costs incurred on uncompleted contracts	$ 112,444	$ 84,563
Estimated earnings	57,834	47,000
Total	170,278	131,563
Less: Billings to date	158,218	122,144
Net under (over) billings	$ 12,060	$ 9,419

Amounts due for billed services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party. An example would be amounts billed to customers under contracts or programs but not paid as of the 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

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