Note 2 - Goodwill and Purchased Intangible Assets (Details Textual) - USD ($) $ in Thousands	3 Months Ended
Mar. 27, 2021	Mar. 28, 2020	Dec. 26, 2020
Transfer From In-Process Technology to Developed Technology	$ 3,700
Amortization of Intangible Assets, Total	9,244	$ 9,538
In-process Technology [Member]
Indefinite-lived Intangible Assets (Excluding Goodwill), Ending Balance	$ 4,100		$ 7,800

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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