Note 4 - Goodwill and Other Intangible Assets (Details Textual) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Apr. 01, 2017
Finite-lived Intangible Assets Acquired	$ 211,600
Amortization of Intangible Assets, Total	11,998	$ 5,944
IXYS Corporation [Member]
Finite-lived Intangible Assets Acquired	$ 211,600

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.

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