Goodwill and Acquired Intangibles (Details 2) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 02, 2021	Sep. 26, 2020	Oct. 02, 2021	Sep. 26, 2020
Amortization of acquired intangibles
Cost of product and maintenance	$ 11,774	$ 11,447	$ 35,774	$ 33,791
Amortization of acquired intangibles	5,000	4,438	14,661	13,234
Total amortization of acquired intangibles	$ 16,774	$ 15,885	$ 50,435	$ 47,025

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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