Business Segment Information - Financial Information by Reportable Segment (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 02, 2016	Jul. 04, 2015	Jul. 02, 2016	Jul. 04, 2015
Segment Reporting Information [Line Items]
Net Revenues	$ 133,437,000	$ 174,845,000	$ 275,585,000	$ 347,765,000
Segment Operating Income	11,512,000	14,562,000	20,623,000	22,985,000
Operating Income	7,266,000	10,839,000	11,559,000	14,466,000
Depreciation and Amortization Expenses	5,476,000	6,514,000	11,331,000	13,428,000
Capital Expenditures	4,947,000	3,367,000	7,348,000	8,195,000
Operating Segments | Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	60,694,000	76,078,000	124,711,000	148,136,000
Segment Operating Income	4,730,000	6,870,000	7,454,000	9,008,000
Depreciation and Amortization Expenses	1,775,000	2,111,000	3,832,000	4,624,000
Capital Expenditures	4,540,000	2,417,000	6,594,000	5,751,000
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	72,743,000	98,767,000	150,874,000	199,629,000
Segment Operating Income	6,782,000	7,692,000	13,169,000	13,977,000
Depreciation and Amortization Expenses	3,668,000	4,361,000	7,429,000	8,720,000
Capital Expenditures	407,000	948,000	754,000	2,438,000
Corporate Administration
Segment Reporting Information [Line Items]
Corporate General and Administrative Expenses	(4,246,000)	(3,723,000)	(9,064,000)	(8,519,000)
Depreciation and Amortization Expenses	33,000	42,000	70,000	84,000
Capital Expenditures	$ 0	$ 2,000	0	$ 6,000
Adjustments for Error Correction | Corporate Administration
Segment Reporting Information [Line Items]
Corporate General and Administrative Expenses			$ (0.7)