Changes in Accumulated Other Comprehensive Income by Component (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 89,624	$ 82,663
Other comprehensive income, net of tax	106	76
Ending balance	89,087	78,518
Foreign currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	405	535
Other comprehensive income (loss) before reclassification	61	104
Amounts reclassified from other comprehensive income (loss)	0	0
Other comprehensive income, net of tax	61	104
Ending balance	466	639
Unrealized holding gains (losses) on available- for-sale investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(27)	(45)
Other comprehensive income (loss) before reclassification	45	(28)
Amounts reclassified from other comprehensive income (loss)	0	0
Other comprehensive income, net of tax	45	(28)
Ending balance	18	(73)
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	378	490
Other comprehensive income (loss) before reclassification	106	76
Amounts reclassified from other comprehensive income (loss)	0	0
Other comprehensive income, net of tax	106	76
Ending balance	$ 484	$ 566