Interim Financial Statements - Additional Information (Detail) $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Facility	Sep. 30, 2017 USD ($)
Interim Reporting [Line Items]
Number of manufacturing facilities | Facility				51
Net profit change on contracts (less than)		$ (13,784)	$ 125,961	$ (44,277)	$ 112,234
Cash paid for debt prepayment	$ 31,600
Right-of-use asset and lease liability to exceed				50,000
Maximum | Accounting Standards Update 2014-09
Interim Reporting [Line Items]
Net profit change on contracts (less than)				$ 100