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Supplemental Quarterly Financial Data (Unaudited) - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Apr. 02, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Sep. 30, 2017
Sep. 11, 2017
Segment Reporting Information [Line Items]              
Tax Cuts and Jobs Act of 2017, provisional income tax benefit $ 13,000            
Restructuring Charges 8,800   $ 8,360 $ 182 $ 2,125    
Pittsburgh and Miltec Operations [Member]              
Segment Reporting Information [Line Items]              
Gain (loss) on disposition of assets   $ 18,800          
Lightning Diversion Systems, Inc.              
Segment Reporting Information [Line Items]              
Equity interest acquired           100.00% 100.00%
Cost of Sales              
Segment Reporting Information [Line Items]              
Restructuring Charges $ 500