Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2016 USD ($)	Oct. 03, 2015 USD ($)	Oct. 01, 2016 USD ($) Segment	Oct. 03, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment			5
Product Sales	$ 591,903	$ 559,918	$ 1,752,400	$ 1,741,965
Royalty Revenues	52	736	212	2,595
Total Revenue	591,955	560,654	1,752,612	1,744,560
Gross Margin	153,901	130,144	437,338	416,664
Segment Operating Income	124,736	95,162	336,994	310,437
Restructuring and severance Costs	(1,197)	(2,324)	(12,139)	(9,394)
Impairment of Intangible Assets	1,559	57,600	1,559	57,600
Impairment of goodwill	0	5,380	0	5,380
Operating income	57,229	(24,155)	147,185	67,573
Unallocated Other Income (Expense)	(6,545)	(8,787)	(11,649)	(17,264)
Income before taxes	50,684	(32,942)	135,536	50,309
MOSFETS Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	101,687	109,446	304,839	322,553
Royalty Revenues	0	0	0	11
Total Revenue	101,687	109,446	304,839	322,564
Gross Margin	16,443	16,795	40,914	45,261
Segment Operating Income	7,493	6,839	12,671	16,506
Diodes Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	141,127	123,922	418,629	399,155
Royalty Revenues	0	0	0	0
Total Revenue	141,127	123,922	418,629	399,155
Gross Margin	36,444	27,508	106,364	88,998
Segment Operating Income	31,832	21,628	90,025	70,641
Optoelectronic Components Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	72,801	70,008	203,635	211,610
Royalty Revenues	0	0	0	0
Total Revenue	72,801	70,008	203,635	211,610
Gross Margin	24,250	22,969	65,049	69,483
Segment Operating Income	20,340	17,673	49,838	53,923
Resistors And Inductors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	191,989	172,995	568,122	538,173
Royalty Revenues	52	736	212	2,584
Total Revenue	192,041	173,731	568,334	540,757
Gross Margin	58,768	49,843	171,808	162,034
Segment Operating Income	51,861	41,404	147,315	135,399
Capacitors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	84,299	83,547	257,175	270,474
Royalty Revenues	0	0	0	0
Total Revenue	84,299	83,547	257,175	270,474
Gross Margin	17,996	13,029	53,203	50,888
Segment Operating Income	13,210	7,618	37,145	33,968
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	(64,751)	(54,013)	(176,111)	(170,490)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	124,736	95,162	336,994	310,437
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Restructuring and severance Costs	(1,197)	(2,324)	(12,139)	(9,394)
Impairment of Intangible Assets	(1,559)	(57,600)	(1,559)	(57,600)
Impairment of goodwill	0	(5,380)	0	(5,380)
Unallocated Other Income (Expense)	$ (6,545)	$ (8,787)	$ (11,649)	$ (17,264)