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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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Sep. 29, 2018	Jun. 30, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 29, 2018
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization, intangible assets	$ 124,000			$ 124,000		$ 114,500
Amortization of acquired intangible assets	3,403	$ 3,837		10,209	$ 14,246
Amortization of impairment charge relating to intangible assets	0	586	$ 11,900	0	12,486
Research and development
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangible assets	14	14		41	264
Amortization of acquired intangible assets
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangible assets	$ 3,389	$ 3,823		$ 10,168	$ 13,982