Goodwill and Acquired Intangibles (Details 2) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Amortization of acquired intangibles
Cost of product and maintenance	$ 11,299	$ 9,991	$ 21,153	$ 20,268
Amortization of acquired intangibles	3,159	3,518	6,467	7,148
Total amortization of acquired intangibles	$ 14,458	$ 13,509	$ 27,620	$ 27,416

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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