Note 4 - Acquisition of Businesses - Preliminary Price Allocation (Details) - USD ($) $ in Thousands	Oct. 01, 2016	Aug. 29, 2016	Apr. 04, 2016	Mar. 25, 2016	Oct. 01, 2015	Jan. 02, 2016	Mar. 25, 2015
TVS Diode, Thyristor and IGBT Business [Member] | Customer Relationships [Member]
Intangible assets, other than goodwill		$ 31,650
TVS Diode, Thyristor and IGBT Business [Member] | Patented and Unpatented Technologies [Member]
Intangible assets, other than goodwill		10,250
TVS Diode, Thyristor and IGBT Business [Member] | Noncompete Agreements [Member]
Intangible assets, other than goodwill		2,500
TVS Diode, Thyristor and IGBT Business [Member]
Cash		104,000
Current assets, net		4,616
Goodwill		54,984
		104,000
Cash, net of acquired cash		104,000
Total purchase consideration		104,000
Current assets, net		$ 4,616
Menber's S.p.A. [Member] | Customer Relationships [Member]
Intangible assets, other than goodwill			$ 3,050
Menber's S.p.A. [Member] | Patented and Unpatented Technologies [Member]
Intangible assets, other than goodwill			224
Menber's S.p.A. [Member] | Trademarks and Trade Names [Member]
Intangible assets, other than goodwill			1,849
Menber's S.p.A. [Member]
Cash	$ 18,900		18,909
Current assets, net			13,560
Goodwill			7,651
			19,162
Cash, net of acquired cash	18,900		18,909
Additional consideration payable			253
Total purchase consideration			19,162
Property, plant and equipment			1,693
Current liabilities			(7,421)
Other non-current liabilities			(1,444)
Acquired cash to be returned to seller			253
Current assets, net			13,560
Other non-current liabilities			$ (1,444)
PolySwitch [Member] | Customer Relationships [Member]
Intangible assets, other than goodwill				$ 39,720
PolySwitch [Member] | Patented and Unpatented Technologies [Member]
Intangible assets, other than goodwill				56,425
PolySwitch [Member]
Cash				342,300
Current assets, net				59,751
Goodwill				163,635
				347,971
Cash, net of acquired cash				342,300
Additional consideration payable				5,719
Total purchase consideration				347,971
Property, plant and equipment				52,025
Current liabilities				(37,068)
Other non-current liabilities				(1,518)
Original consideration				350,000
Post closing consideration adjustment received				(2,029)
Acquired cash				(5,719)
Acquired cash to be returned to seller				5,719
Current assets, net				59,751
Land lease				4,290
Other long-term assets							$ 10,711
Other non-current liabilities				$ (1,518)
Sigmar [Member] | Patents [Member]
Intangible assets, other than goodwill					$ 2,845
Sigmar [Member]
Cash					5,788
Current assets, net					4,011
Goodwill					2,552
					6,689
Cash, net of acquired cash					5,788
Additional consideration payable					901
Total purchase consideration					6,689
Property, plant and equipment					1,097
Current liabilities					(1,478)
Other non-current liabilities					(2,568)
Acquired cash to be returned to seller					901
Current assets, net					4,011
Cash					230
Other non-current liabilities					$ (2,568)
Goodwill	$ 409,527					$ 189,767