Goodwill and Acquired Intangibles (Details 2) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Amortization of acquired intangibles
Cost of product and maintenance	$ 9,505	$ 10,165	$ 29,773	$ 31,611
Amortization of acquired intangibles	3,470	3,453	10,618	11,145
Total amortization of acquired intangibles	$ 12,975	$ 13,618	$ 40,391	$ 42,756

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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