Business Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Segment Reporting Information [Line Items]
Net Revenues	$ 140,938	$ 133,437	$ 277,235	$ 275,585
Operating Income	6,471	7,266	10,571	11,559
Depreciation and Amortization Expenses	5,748	5,476	11,530	11,331
Capital Expenditures	9,258	4,947	15,879	7,348
Operating Segments
Segment Reporting Information [Line Items]
Operating Income	10,869	11,512	20,605	20,623
Operating Segments | Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	59,112	60,694	116,687	124,711
Operating Income	2,049	4,730	4,681	7,454
Depreciation and Amortization Expenses	2,307	1,775	4,659	3,832
Capital Expenditures	7,580	4,540	12,768	6,594
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	81,826	72,743	160,548	150,874
Operating Income	8,820	6,782	15,924	13,169
Depreciation and Amortization Expenses	3,439	3,668	6,862	7,429
Capital Expenditures	1,030	407	2,463	754
Segment Reconciling Items
Segment Reporting Information [Line Items]
Corporate General and Administrative Expenses	(4,398)	(4,246)	(10,034)	(9,064)
Corporate Administration
Segment Reporting Information [Line Items]
Depreciation and Amortization Expenses	2	33	9	70
Capital Expenditures	$ 648	$ 0	$ 648	$ 0