Components of and Changes in Accumulated Other Comprehensive Income, Net of Related Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 650,672
Other comprehensive (loss)	$ 715	$ 631	(1,407)	$ 1,381
Ending Balance	723,841		723,841
Unrealized Holding Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(144)
Other comprehensive (loss)			(876)
Ending Balance	(1,020)		(1,020)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(3,018)
Other comprehensive (loss)			(531)
Ending Balance	(3,549)		(3,549)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(3,162)
Other comprehensive (loss)			(1,407)
Ending Balance	$ (4,569)		$ (4,569)