Equity - Changes in Accumulated Other Comprehensive Income by Component (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 88,347	$ 78,586	$ 89,624	$ 82,663
Other comprehensive loss, net of tax	(84)	(73)	(7)	(119)
Ending balance	89,186	79,342	89,186	79,342
Foreign currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	405	495	405	535
Other comprehensive income (loss) before reclassification	(87)	(86)	(87)	(126)
Other comprehensive loss, net of tax	(87)	(86)	(87)	(126)
Ending balance	318	409	318	409
Unrealized holding gains (losses) on available- for-sale investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	50	(51)	(27)	(45)
Other comprehensive income (loss) before reclassification	3	13	80	7
Other comprehensive loss, net of tax	3	13	80	7
Ending balance	53	(38)	53	(38)
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	455	444	378	490
Other comprehensive income (loss) before reclassification	(84)	(73)	(7)	(119)
Other comprehensive loss, net of tax	(84)	(73)	(7)	(119)
Ending balance	$ 371	$ 371	$ 371	$ 371

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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