Components of and Changes in Accumulated Other Comprehensive Income, Net of Related Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 650,672
Other comprehensive (loss)	$ (1,733)	$ 549	(2,122)	$ 750
Ending Balance	657,708		657,708
Unrealized Holding Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(144)
Other comprehensive (loss)			(883)
Ending Balance	(1,027)		(1,027)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(3,018)
Other comprehensive (loss)			(1,239)
Ending Balance	(4,257)		(4,257)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(3,162)
Other comprehensive (loss)			(2,122)
Ending Balance	$ (5,284)		$ (5,284)