Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Apr. 02, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Balance at beginning of period		$ 142,742		$ 142,742	$ 141,407
Exchange rate effects				(557)	1,335
Balance at end of period				147,480	142,742	$ 141,407
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Subject to Amortization				168,232	245,454
Accumulated amortization				(102,544)	(175,700)
Net Intangible Assets Subject to Amortization				65,688	69,754
Intangible assets, net				65,688	69,754
Amortization expense (excluding capitalized software)				11,807	14,263	14,842
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
2019				8,424
2020				7,433
2021				6,543
2022				5,891
2023				5,668
Sonntag [Member]
Goodwill [Roll Forward]
Goodwill acquired during period			$ 3,485
Capella Microsystems (Taiwan) Inc. [Member]
Goodwill [Roll Forward]
Impairment of Long-Lived Assets Held-for-use							$ 1,559
UltraSource [Member]
Goodwill [Roll Forward]
Goodwill acquired during period		4,227		4,227
Other intangible assets related to acquisitions		6,500
EuroPower [Member]
Goodwill [Roll Forward]
Goodwill acquired during period	$ 1,068			1,068
Resistors And Inductors Segment [Member]
Goodwill [Roll Forward]
Balance at beginning of period		45,893		45,893	44,558
Exchange rate effects				(557)	1,335
Balance at end of period				50,631	45,893	44,558
Resistors And Inductors Segment [Member] | UltraSource [Member]
Goodwill [Roll Forward]
Goodwill acquired during period				4,227
Resistors And Inductors Segment [Member] | EuroPower [Member]
Goodwill [Roll Forward]
Goodwill acquired during period				1,068
Optoelectronic Components Segment [Member]
Goodwill [Roll Forward]
Balance at beginning of period		$ 96,849		96,849	96,849
Exchange rate effects				0	0
Balance at end of period				96,849	96,849	$ 96,849
Optoelectronic Components Segment [Member] | UltraSource [Member]
Goodwill [Roll Forward]
Goodwill acquired during period				0
Optoelectronic Components Segment [Member] | EuroPower [Member]
Goodwill [Roll Forward]
Goodwill acquired during period				0
Patents and Acquired Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Subject to Amortization				32,854	71,596
Accumulated amortization				(26,469)	(63,868)
Capitalized Software [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Subject to Amortization				53,218	54,325
Accumulated amortization				(49,288)	(50,246)
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Subject to Amortization				59,119	63,655
Accumulated amortization				(19,958)	(26,622)
Tradenames [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Subject to Amortization				23,041	55,272
Accumulated amortization				(6,829)	(34,378)
Non-competition Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Subject to Amortization				0	606
Accumulated amortization				$ 0	$ (586)