Segment Information (Details) $ in Thousands	3 Months Ended
	Apr. 01, 2017 USD ($) Segment	Apr. 02, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	5
Product Sales	$ 606,252	$ 570,528
Royalty Revenues	6	78
Total Revenue	606,258	570,606
Gross Margin	160,875	137,309
Segment Operating Income	129,484	101,101
Restructuring and severance Costs	(1,469)	(6,475)
Operating income	64,688	40,548
Unallocated Other Income (Expense)	(14,246)	(2,076)
Income before taxes	50,442	38,472
MOSFETS Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	105,529	100,933
Royalty Revenues	0	0
Total Revenue	105,529	100,933
Gross Margin	20,676	12,587
Segment Operating Income	11,761	2,618
Diodes Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	144,895	135,384
Royalty Revenues	0	0
Total Revenue	144,895	135,384
Gross Margin	37,529	32,662
Segment Operating Income	32,739	26,643
Optoelectronic Components Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	65,682	62,775
Royalty Revenues	0	0
Total Revenue	65,682	62,775
Gross Margin	22,301	19,181
Segment Operating Income	16,915	13,654
Resistors And Inductors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	200,377	183,416
Royalty Revenues	6	78
Total Revenue	200,383	183,494
Gross Margin	61,170	55,784
Segment Operating Income	53,897	46,883
Capacitors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	89,769	88,020
Royalty Revenues	0	0
Total Revenue	89,769	88,020
Gross Margin	19,199	17,095
Segment Operating Income	14,172	11,303
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	(63,327)	(54,078)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	129,484	101,101
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Restructuring and severance Costs	(1,469)	(6,475)
Unallocated Other Income (Expense)	$ (14,246)	$ (2,076)