Business Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Segment Reporting Information [Line Items]
Net Revenues	$ 154,827	$ 140,938	$ 305,282	$ 277,235
Operating Income	5,596	6,623	10,851	10,875
Depreciation and Amortization Expenses	6,334	5,748	12,315	11,530
Capital Expenditures	2,769	9,258	7,032	15,879
Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	70,325	59,112	138,372	116,687
Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	84,502	81,826	166,910	160,548
Operating Segments
Segment Reporting Information [Line Items]
Operating Income	13,694	11,021	23,829	20,909
Operating Segments | Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	70,325	59,112	138,372	116,687
Operating Income	5,026	2,127	9,417	4,837
Depreciation and Amortization Expenses	2,618	2,307	4,934	4,659
Capital Expenditures	1,101	7,580	2,630	12,768
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	84,502	81,826	166,910	160,548
Operating Income	8,668	8,894	14,412	16,072
Depreciation and Amortization Expenses	3,683	3,439	7,315	6,862
Capital Expenditures	1,478	1,030	4,212	2,463
Segment Reconciling Items
Segment Reporting Information [Line Items]
Corporate General and Administrative Expenses	(8,098)	(4,398)	(12,978)	(10,034)
Corporate Administration
Segment Reporting Information [Line Items]
Depreciation and Amortization Expenses	33	2	66	9
Capital Expenditures	$ 190	$ 648	$ 190	$ 648