Business Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Segment Reporting Information [Line Items]
Net Revenues	$ 150,455	$ 136,297
Operating Income	5,256	4,252
Depreciation and Amortization Expenses	5,981	5,782
Capital Expenditures	4,263	6,621
Operating Segments
Segment Reporting Information [Line Items]
Operating Income	10,135	9,888
Operating Segments | Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	68,046	57,575
Operating Income	4,391	2,784
Depreciation and Amortization Expenses	2,316	2,352
Capital Expenditures	1,529	5,188
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	82,409	78,722
Operating Income	5,744	7,104
Depreciation and Amortization Expenses	3,632	3,423
Capital Expenditures	2,734	1,433
Segment Reconciling Items
Segment Reporting Information [Line Items]
Corporate General and Administrative Expenses	(4,879)	(5,636)
Corporate Administration
Segment Reporting Information [Line Items]
Depreciation and Amortization Expenses	33	7
Capital Expenditures	$ 0	$ 0