Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Oct. 01, 2016 USD ($)	Sep. 30, 2017 USD ($) Segment	Oct. 01, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment			5
Product Sales	$ 677,875	$ 591,903	$ 1,928,983	$ 1,752,400
Royalty Revenues	8	52	50	212
Total Revenue	677,883	591,955	1,929,033	1,752,612
Gross Margin	189,273	153,901	523,111	437,338
Segment Operating Income	159,349	124,736	431,936	336,994
Restructuring and severance Costs	(3,244)	(1,197)	(5,194)	(12,139)
Impairment of Intangible Assets	0	(1,559)	0	(1,559)
Operating income	92,328	57,229	239,052	147,185
Unallocated Other Income (Expense)	(6,140)	(6,545)	(26,713)	(11,649)
Income before taxes	86,188	50,684	212,339	135,536
MOSFETS Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	126,522	101,687	346,086	304,839
Royalty Revenues	0	0	0	0
Total Revenue	126,522	101,687	346,086	304,839
Gross Margin	32,307	16,443	78,298	40,914
Segment Operating Income	23,391	7,493	51,789	12,671
Diodes Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	160,711	141,127	461,323	418,629
Royalty Revenues	0	0	0	0
Total Revenue	160,711	141,127	461,323	418,629
Gross Margin	42,942	36,444	121,601	106,364
Segment Operating Income	37,991	31,832	106,906	90,025
Optoelectronic Components Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	76,740	72,801	216,260	203,635
Royalty Revenues	0	0	0	0
Total Revenue	76,740	72,801	216,260	203,635
Gross Margin	28,901	24,250	76,668	65,049
Segment Operating Income	25,012	20,340	63,401	49,838
Resistors And Inductors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	217,593	191,989	627,116	568,122
Royalty Revenues	8	52	50	212
Total Revenue	217,601	192,041	627,166	568,334
Gross Margin	65,541	58,768	188,801	171,808
Segment Operating Income	58,267	51,861	166,852	147,315
Capacitors Segment [Member]
Segment Reporting Information [Line Items]
Product Sales	96,309	84,299	278,198	257,175
Royalty Revenues	0	0	0	0
Total Revenue	96,309	84,299	278,198	257,175
Gross Margin	19,582	17,996	57,743	53,203
Segment Operating Income	14,688	13,210	42,988	37,145
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	(63,777)	(64,751)	(187,690)	(176,111)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment Operating Income	159,349	124,736	431,936	336,994
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Restructuring and severance Costs	(3,244)	(1,197)	(5,194)	(12,139)
Impairment of Intangible Assets	0	(1,559)	0	(1,559)
Unallocated Other Income (Expense)	$ (6,140)	$ (6,545)	$ (26,713)	$ (11,649)