Note 12 - Segment Information - Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Revenue		$ 459,183	$ 313,355	$ 876,996	$ 598,797
Depreciation and amortization		26,190	15,617	49,802	30,690
Operating income		59,622	60,270	97,193	109,123
Interest expense		5,782	3,281	11,205	6,401
Foreign exchange loss (gain)		3,200	(558)	(7,354)	(2,115)
Other expense (income), net		(1,678)	190	(3,621)	52
Income before income taxes		52,318	57,357	96,963	104,785
Electronics [Member]
Revenue		299,357	169,387	563,768	323,154
Depreciation and amortization		15,651	8,707	29,329	17,095
Operating income		67,311	42,967	121,275	78,173
Automotive [Member]
Revenue		127,172	116,457	253,302	224,297
Depreciation and amortization		5,969	5,580	11,939	10,950
Operating income		15,711	15,713	34,102	30,778
Industrial [Member]
Revenue		32,654	27,511	59,926	51,346
Depreciation and amortization		1,467	1,330	2,927	2,645
Operating income		5,279	1,905	9,988	2,012
Other Segments [Member]
Depreciation and amortization		3,103		5,607
Operating income	[1]	$ (28,679)	$ (315)	$ (68,172)	$ (1,840)

[1] Included in "Other" Operating income (loss) for the 2018 second quarter is $24.4 million ($63.2 million year-to-date) of charges primarily related to IXYS acquisition and include $19.0 million ($36.9 million year-to-date) of purchase accounting inventory charges, $2.3 million ($14.1 million year-to-date) in acquisition-related and integration costs primarily related to legal, accounting and other expenses associated with the acquisition of IXYS, $3.1 million ($5.6 million year-to-date) in backlog amortization costs, stock compensation expense recognized immediately upon close for converted IXYS options related to prior services periods $4.5 million year-to-date and other charges of $2.1 million year-to-date. In addition, there were $3.2 million ($3.9 million year-to-date) of severance and other restructuring charges and $1.1 million of impairment charges ($1.1 million year-to-date) associated with the closure of the Radio Pulse and Custom businesses, respectively.