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. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 542,557
Other comprehensive income	$ 631	$ (215)	1,381	$ 1,019
Ending Balance	650,355		650,355
Unrealized Holding (Losses) Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(71)
Other comprehensive income			251
Ending Balance	180		180
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(3,018)
Other comprehensive income			1,130
Ending Balance	(1,888)		(1,888)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(3,089)
Other comprehensive income			1,381
Ending Balance	$ (1,708)		$ (1,708)