Restructuring and Related Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Apr. 04, 2015	Mar. 29, 2014	Dec. 31, 2014	Dec. 31, 2013
Restructuring Reserve [Roll Forward]
Restructuring and severance costs	$ 1,410	$ 6,404
Expected Restructuring Costs	32,000
MOSFETs Enhanced Competitiveness Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Current	8,195
Restructuring Reserve [Roll Forward]
Restructuring and severance costs	1,353	1,727	6,025	2,328
Cash paid	(388)		(856)	(267)
Balance at end of period	8,195		7,230	2,061
Balance at beginning of period	7,230	2,061	2,061
Term of restructuring program	2 years
Expected Restructuring Costs	16,000
Voluntary Separation/Retirement Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Current	3,229
Restructuring Reserve [Roll Forward]
Restructuring and severance costs	57	4,677	12,792	486
Cash paid	(1,216)		(8,054)	(98)
Foreign currency translation	(286)		(455)	3
Balance at end of period	3,229		4,674	391
Balance at beginning of period	4,674	391	391
Modules Product Transfer [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Current	842
Restructuring Reserve [Roll Forward]
Restructuring and severance costs	0	0	2,080
Cash paid	(525)		(464)
Foreign currency translation	(128)		(121)
Balance at end of period	842		1,495
Balance at beginning of period	$ 1,495