Segment Reporting (Schedule of Segment Reporting Information, by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Net Sales:
Net sales	$ 203,386	$ 208,853	$ 643,924	$ 655,385
Operating Income (Loss)
Total operating income (loss)	9,323	18,312	70,208	54,340
Total income before income taxes	8,111	16,759	68,433	52,312
Depreciation and Amortization:
Total depreciation and amortization	7,886	7,066	22,733	21,942
Interest Expense, net:
Total interest expense, net	1,149	1,155	3,153	3,679
Interest Expense, net:
Total interest expense, net	1,149	1,155	3,153	3,679
Capital Expenditures:
Capital expenditures	10,574	5,971	28,053	22,816
Long-Lived Assets	262,762		262,762		$ 239,342
Total Assets:
Total assets	594,004		594,004		559,519
Intersegment Eliminations [Member]
Net Sales:
Net sales	(10,052)	(10,623)	(33,044)	(35,530)
Total Assets:
Total assets	(321,865)		(321,865)		(322,866)
Control Devices [Member]
Net Sales:
Net sales	108,690	108,402	332,876	333,715
Operating Income (Loss)
Total operating income (loss)	9,767	16,297	66,082	51,336
Depreciation and Amortization:
Total depreciation and amortization	3,310	3,070	9,601	8,762
Interest Expense, net:
Total interest expense, net	189	19	566	56
Capital Expenditures:
Capital expenditures	3,175	3,938	10,709	12,996
Total Assets:
Total assets	194,016		194,016		175,708
Control Devices [Member] | Operating Segments [Member]
Net Sales:
Net sales	109,875	109,958	338,000	339,933
Control Devices [Member] | Inter-Segment Sales [Member]
Net Sales:
Net sales	1,185	1,556	5,124	6,218
Electronics [Member]
Net Sales:
Net sales	78,154	81,587	260,560	261,928
Operating Income (Loss)
Total operating income (loss)	7,661	8,951	24,247	25,107
Depreciation and Amortization:
Total depreciation and amortization	2,708	2,213	7,615	6,756
Interest Expense, net:
Total interest expense, net	79	32	198	89
Capital Expenditures:
Capital expenditures	5,473	725	12,567	4,892
Total Assets:
Total assets	276,763		276,763		265,838
Electronics [Member] | Operating Segments [Member]
Net Sales:
Net sales	87,021	90,654	288,474	291,238
Electronics [Member] | Inter-Segment Sales [Member]
Net Sales:
Net sales	8,867	9,067	27,914	29,310
PST [Member]
Net Sales:
Net sales	16,542	18,864	50,488	59,742
Operating Income (Loss)
Total operating income (loss)	(451)	668	6,633	1,553
Depreciation and Amortization:
Total depreciation and amortization	1,571	1,583	4,791	5,828
Interest Expense, net:
Total interest expense, net	69	230	118	762
Capital Expenditures:
Capital expenditures	1,243	522	2,867	2,477
Total Assets:
Total assets	85,739		85,739		81,002
PST [Member] | Operating Segments [Member]
Net Sales:
Net sales	16,542	18,864	50,494	59,744
PST [Member] | Inter-Segment Sales [Member]
Net Sales:
Net sales			6	2
Unallocated Corporate [Member]
Operating Income (Loss)
Total operating income (loss)	(7,654)	(7,604)	(26,754)	(23,656)
Depreciation and Amortization:
Total depreciation and amortization	297	200	726	596
Interest Expense, net:
Total interest expense, net	812	874	2,271	2,772
Capital Expenditures:
Capital expenditures	683	$ 786	1,910	$ 2,451
Total Assets:
Total assets	$ 359,351		$ 359,351		$ 359,837