Business Segment Information - Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net Revenues	$ 142,258	$ 138,690	$ 140,938	$ 136,297	$ 142,486	$ 132,571	$ 133,437	$ 142,148	$ 558,183	$ 550,642	$ 666,011
Segment Operating Income (Loss)									36,417	45,480	(57,482)
Corporate General and Administrative Expenses									(21,392)	(16,912)	(17,827)
Operating Income (Loss)									15,025	28,568	(75,309)
Depreciation and amortization									22,845	22,860	26,846
Capital Expenditures									26,473	18,693	15,988
Operating Segments | Structural Systems
Segment Reporting Information [Line Items]
Net Revenues									241,460	246,465	273,319
Segment Operating Income (Loss)									5,477	16,497	(53,010)
Depreciation and amortization									8,860	8,688	9,417
Capital Expenditures									20,679	15,661	11,559
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues									316,723	304,177	392,692
Segment Operating Income (Loss)									30,940	28,983	(4,472)
Depreciation and amortization									13,888	14,087	17,267
Capital Expenditures									5,019	3,032	4,419
Corporate Administration
Segment Reporting Information [Line Items]
Depreciation and amortization									97	85	162
Capital Expenditures									$ 775	$ 0	$ 10