Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Apr. 01, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 33,104	$ 37,217
Available-for-sale investments:
Net unrealized gain (loss), net of tax of $268 and ($114) in 2019 and 2018, respectively	2,251	(1,192)
Reclassification of net realized (gain) loss into current operations	(40)	(22)
Net change related to available-for-sale investments	2,211	(1,214)
Foreign currency translation adjustments:
Foreign currency translation adjustments	218	4,056
Other comprehensive income (loss), net of tax	2,429	2,842
Total comprehensive income	$ 35,533	$ 40,059

Currency translation adjustments [Abstract]

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