Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 5,764	$ 7,883	$ 19,404	$ 17,381
Other comprehensive income (loss):
Change in foreign currency translation adjustment	764	519	3,470	2,018
Net change on unrealized gains (losses) on available-for-sale investments	15	1	(2)	73
Other comprehensive income:	779	520	3,468	2,091
Comprehensive income	$ 6,543	$ 8,403	$ 22,872	$ 19,472

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities and unrealized holding gain (loss) related to transfers of securities into the available-for-sale classification and out of the held-to-maturity classification.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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