Business Segment Information - Financial Information by Reportable Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net Revenues	$ 628,941	$ 721,088	$ 629,307
Operating Income (Loss)	45,506	56,233	23,918
Depreciation and Amortization Expenses	28,850	28,305	25,296
Capital Expenditures	13,607	18,846	16,337
Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	392,633	360,373
Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	236,308	360,715
Operating Segments
Segment Reporting Information [Line Items]
Operating Income (Loss)	71,478	85,449	49,979
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Net Revenues	392,633	360,373	337,868
Operating Income (Loss)	51,894	38,613	30,916
Depreciation and Amortization Expenses	14,038	14,170	14,223
Capital Expenditures	5,037	5,508	6,719
Operating Segments | Structural Systems
Segment Reporting Information [Line Items]
Net Revenues	236,308	360,715	291,439
Operating Income (Loss)	19,584	46,836	19,063
Depreciation and Amortization Expenses	14,559	13,663	10,525
Capital Expenditures	8,570	13,338	9,104
Corporate Administration
Segment Reporting Information [Line Items]
Corporate General and Administrative Expenses	(25,972)	(29,216)	(26,061)
Depreciation and Amortization Expenses	253	472	548
Capital Expenditures	$ 0	$ 0	$ 514