Note 2 - Goodwill and Purchased Intangible Assets (Details Textual) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Mar. 28, 2020	Dec. 25, 2021	Sep. 26, 2020	Dec. 25, 2021	Dec. 26, 2020	Dec. 28, 2019
Goodwill, Impairment Loss	$ 0	$ 0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)				$ 100	$ 11,249	$ 0
Amortization of Intangible Assets, Total				35,414	38,746	$ 39,590
Finite-Lived Intangible Asset, Expected Amortization, Year One		34,800		34,800
Finite-Lived Intangible Asset, Expected Amortization, Year Two		34,800		34,800
Finite-Lived Intangible Asset, Expected Amortization, Year Three		34,800		34,800
Finite-Lived Intangible Asset, Expected Amortization, Year Four		26,100		26,100
Finite-Lived Intangible Asset, Expected Amortization, Year Five		19,300		19,300
Finite-Lived Intangible Asset, Expected Amortization, after Year Five		27,400		$ 27,400
In-process Technology [Member]
Indefinite-lived Intangible Assets (Excluding Goodwill), Ending Balance					7,800
Indefinite-lived In Process Research and Development [Member]
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	$ 3,900	$ 100	$ 7,300		$ 11,200