Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 30, 2019	Mar. 31, 2018	Mar. 30, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (43,513)	$ 7,922	$ (22,528)	$ 21,799
Other comprehensive income (loss), net of tax:
Realized and unrealized hedge gain (loss) arising during the period, net of tax of $0.2 million and $0.3 million in the second quarter of 2019 and 2018, respectively, and $0.2 million and $0.4 million in the first six months of 2019 and 2018, respectively	(2,955)	(2,046)	826	(2,959)
Net hedge (gain) loss reclassified into earnings, net of tax of $0 million and $0.2 million in the second quarter of 2019 and 2018, respectively, and $0.1 million and $0.3 million in the first six months of 2019 and 2018, respectively	0	1,511	(549)	2,084
Realized and unrealized gain (loss) on hedging instruments	(2,955)	(535)	277	(875)
Foreign currency translation adjustment, net of tax of $0 for each period	(4,033)	7,540	(11,602)	12,769
Unrealized gain (loss) on marketable securities, net of tax of $0 for each period	289	(267)	302	(446)
Amortization of net actuarial pension loss included in net income, net of tax of $0.2 million and $0.2 million in the second quarter of 2019 and 2018, respectively and $0.3 million and $0.3 million in the first six months of 2019 and 2018, respectively	428	386	858	757
Change in unamortized pension loss during the period related to changes in foreign currency	345	(465)	626	(728)
Other comprehensive income (loss)	(5,926)	6,659	(9,539)	11,477
Comprehensive income (loss)	$ (49,439)	$ 14,581	$ (32,067)	$ 33,276