Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 30, 2019	Mar. 31, 2018
Stock-based compensation costs
Stock based compensation costs	$ 12,584	$ 12,192
Income tax benefit	3,320	5,219
Share based compensation costs after tax	9,264	6,973
Total unrecognized compensation costs related to awards	$ 98,800
Weighted-average period of recognition of unrecognized compensation costs	2 years 3 months 18 days
Cost of revenues
Stock-based compensation costs
Stock based compensation costs	$ 318	296
Research and development
Stock-based compensation costs
Stock based compensation costs	6,097	5,769
Selling, general and administrative
Stock-based compensation costs
Stock based compensation costs	$ 6,169	$ 6,127

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The amount of expense, net of income tax, recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Unrecognized cost of unvested share-based compensation awards.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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