Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Statement Of Comprehensive Income [Abstract]
Net unrealized (income) loss on hedging derivatives, tax	$ (1,100)	$ 0	$ (600)	$ (1,000)
Reclassification adjustment for loss on settlement of hedging derivatives included in net income, tax effect	100	0	100	300
Foreign currency translation gain (loss) tax	$ 0	$ 0	$ 0	$ 0