Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Net income	$ 42,326	$ 48,638	$ 78,354	$ 87,530
Other comprehensive income (loss):
Pension and postemployment liability adjustments (net of tax expense (benefit) of $42 and $23 for the three months ended 2018 and 2017, and ($18) and $55 for the six months ended 2018 and 2017, respectively)	590	(19)	402	(200)
Pension and postemployment reclassification adjustments (net of tax expense (benefit) of ($5) and $28 for the three months ended 2018 and 2017, and ($11) and $64 for the six months ended 2018 and 2017, respectively)	176	(80)	361	(181)
Unrealized gain (loss) on investments		(472)		475
Foreign currency translation adjustments	(16,708)	(3,582)	(16,984)	1,380
Comprehensive income	$ 26,384	$ 44,485	$ 62,133	$ 89,004