Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017 USD ($)	Jul. 02, 2016 USD ($)	Jul. 01, 2017 USD ($) Segment	Jul. 02, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment			5
Product Sales	$ 644,856	$ 589,969	$ 1,251,108	$ 1,160,497
Royalty Revenues	36	82	42	160
Total Revenue	644,892	590,051	1,251,150	1,160,657
Gross Margin	172,963	146,128	333,838	283,437
Segment Operating Income	143,103	111,157	272,587	212,258
Restructuring and severance Costs	(481)	(4,467)	(1,950)	(10,942)
Operating income	82,036	49,408	146,724	89,956
Unallocated Other Income (Expense)	(6,327)	(3,028)	(20,573)	(5,104)
Income before taxes	75,709	46,380	126,151	84,852
MOSFETS Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	114,035	102,219	219,564	203,152
Royalty Revenues	0	0	0	0
Total Revenue	114,035	102,219	219,564	203,152
Gross Margin	25,315	11,884	45,991	24,471
Segment Operating Income	16,637	2,560	28,398	5,178
Diodes Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	155,717	142,118	300,612	277,502
Royalty Revenues	0	0	0	0
Total Revenue	155,717	142,118	300,612	277,502
Gross Margin	41,130	37,258	78,659	69,920
Segment Operating Income	36,176	31,550	68,915	58,193
Optoelectronic Components Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	73,838	68,059	139,520	130,834
Royalty Revenues	0	0	0	0
Total Revenue	73,838	68,059	139,520	130,834
Gross Margin	25,466	21,618	47,767	40,799
Segment Operating Income	21,474	15,844	38,389	29,498
Resistors And Inductors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	209,146	192,717	409,523	376,133
Royalty Revenues	36	82	42	160
Total Revenue	209,182	192,799	409,565	376,293
Gross Margin	62,090	57,256	123,260	113,040
Segment Operating Income	54,688	48,571	108,585	95,454
Capacitors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	92,120	84,856	181,889	172,876
Royalty Revenues	0	0	0	0
Total Revenue	92,120	84,856	181,889	172,876
Gross Margin	18,962	18,112	38,161	35,207
Segment Operating Income	14,128	12,632	28,300	23,935
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	(60,586)	(57,282)	(123,913)	(111,360)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	143,103	111,157	272,587	212,258
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Restructuring and severance Costs	(481)	(4,467)	(1,950)	(10,942)
Unallocated Other Income (Expense)	$ (6,327)	$ (3,028)	$ (20,573)	$ (5,104)