Accumulated Other Comprehensive Loss - Before and After Tax Amounts for Comprehensive Income (Loss) Components (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 28, 2020	Mar. 29, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 28, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss)	$ 39,110	$ (93,987)	$ 11,071	$ 6,048
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss) before tax	33,454		9,573		$ (52,540)	$ 6,721
Other comprehensive income/(loss), tax	0		0		(7,581)	0
Other comprehensive income/(loss)	33,454		9,573		(60,121)	6,721
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss) before reclassifications before tax	(1,410)		(6,957)		(1,146)	(7,638)
Other comprehensive income/(loss) before reclassifications, tax	351		1,526		284	1,699
Other comprehensive income/(loss) before reclassifications, net of tax	(1,059)		(5,431)		(862)	(5,939)
Amounts reclassified from accumulated other comprehensive income/(loss) before tax					14,774	20,002
Amounts reclassified from accumulated other comprehensive income/(loss), tax					(3,716)	(5,100)
Amounts reclassified from accumulated other comprehensive income/(loss) net of tax					11,058	14,902
Other comprehensive income/(loss) before tax	5,880		2,791		13,628	12,364
Other comprehensive income/(loss), tax	(1,464)		(984)		(3,432)	(3,401)
Other comprehensive income/(loss)	4,416		1,807		10,196	8,963
Defined benefit pension items | Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income/(loss) before tax	7,290		9,748
Amounts reclassified from accumulated other comprehensive income/(loss), tax	(1,815)		(2,510)
Amounts reclassified from accumulated other comprehensive income/(loss) net of tax	5,475		7,238
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss) before reclassifications before tax	1,612		(828)		(5,721)	2,193
Other comprehensive income/(loss) before reclassifications, tax	(394)		297		1,319	(467)
Other comprehensive income/(loss) before reclassifications, net of tax	1,218		(531)		(4,402)	1,726
Other comprehensive income/(loss) before tax	2,421		(719)		(3,522)	1,793
Other comprehensive income/(loss), tax	(591)		238		797	(410)
Other comprehensive income/(loss)	1,830		(481)		(2,725)	1,383
Cash Flow Hedges | Fixed Assets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income/(loss) before tax	0		(56)		0	(101)
Amounts reclassified from accumulated other comprehensive income/(loss), tax	0		0		0	0
Amounts reclassified from accumulated other comprehensive income/(loss) net of tax	0		(56)		0	(101)
Cash Flow Hedges | Net Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from accumulated other comprehensive income/(loss) before tax	809		165		2,199	(299)
Amounts reclassified from accumulated other comprehensive income/(loss), tax	(197)		(59)		(522)	57
Amounts reclassified from accumulated other comprehensive income/(loss) net of tax	612		106		1,677	(242)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income/(loss) before tax	41,755		11,645		(42,434)	20,878
Other comprehensive income/(loss), tax	(2,055)		(746)		(10,216)	(3,811)
Other comprehensive income/(loss)	$ 39,700	$ (92,350)	$ 10,899	$ 6,168	$ (52,650)	$ 17,067