Changes in Accumulated Other Comprehensive Income by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ 73,266
Other comprehensive income (loss) before reclassification	$ 44	$ (33)	122	$ 46
Amounts reclassified from other comprehensive income	0	0	0	0
Other comprehensive income (loss), net of tax	44	(33)	122	46
Ending balance	81,418		81,418
Foreign currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	418	474	343	452
Other comprehensive income (loss) before reclassification	39	(17)	114	5
Amounts reclassified from other comprehensive income	0	0	0	0
Other comprehensive income (loss), net of tax	39	(17)	114	5
Ending balance	457	457	457	457
Unrealized holding losses on available-for-sale investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(19)	17	(22)	(40)
Other comprehensive income (loss) before reclassification	5	(16)	8	41
Amounts reclassified from other comprehensive income	0	0	0	0
Other comprehensive income (loss), net of tax	5	(16)	8	41
Ending balance	(14)	1	(14)	1
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	399	491	321	412
Amounts reclassified from other comprehensive income	0	0	0	0
Ending balance	$ 443	$ 458	$ 443	$ 458