Detail of Certain Balance Sheet Accounts - Contracts in Progress (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Costs incurred on contracts in progress	$ 7,912,999	$ 6,687,484
Estimated earnings, net of estimated losses	1,092,303	766,560
Cost and estimated earnings, total	9,005,302	7,454,044
Less — Billings to date	(8,941,397)	(7,255,582)
Cost and estimated earnings, net	63,905	198,462
Costs and estimated earnings in excess of billings on uncompleted contracts	497,292	473,308
Less — Billings in excess of costs and estimated earnings on uncompleted contracts	$ (433,387)	$ (274,846)

Liability attributable to (i) billings in excess of costs under the percentage of completion contract accounting method representing the difference between contractually invoiced amounts (billings) and revenue recognized based, for example, on costs incurred to estimated total costs at period end or (ii) contractually invoiced amounts (billings) in excess of costs incurred and accumulated under the completed contract accounting method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57807-111642

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57788-111642

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68068069&loc=d3e57795-111642

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