Accumulated other comprehensive loss - Effects on Net Income of Significant Amounts Reclassified from Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Selling, general and administrative expenses									$ 530,867	$ 563,306	$ 507,824
Net sales	$ 1,308,850	$ 1,353,931	$ 1,359,721	$ 1,351,705	$ 1,355,616	$ 1,364,762	$ 1,366,373	$ 1,304,187	5,374,207	5,390,938	5,036,650
Cost of sales									(4,316,378)	(4,349,932)	(4,077,998)
Income before income taxes									380,766	378,531	314,554
Provision for income taxes									(93,269)	(75,008)	(146,589)
Net income									292,668	314,739	$ 177,447
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income									(24,541)	(30,956)
Reclassification out of Accumulated Other Comprehensive Income | Foreign Currency Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Selling, general and administrative expenses									0	(897)
Net income									0	(897)
Reclassification out of Accumulated Other Comprehensive Income | Effect of settlement
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-operating pension costs									(2,377)	(730)
Reclassification out of Accumulated Other Comprehensive Income | Effect of curtailment loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-operating pension costs									0	(256)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of defined benefit pension items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-operating pension costs									(30,382)	(36,689)
Income before income taxes									(32,759)	(37,675)
Provision for income taxes									8,299	7,687
Net income									(24,460)	(29,988)
Reclassification out of Accumulated Other Comprehensive Income | Gains and Losses on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales									1,381	(203)
Cost of sales									(1,488)	95
Income before income taxes									(107)	(108)
Provision for income taxes									26	37
Net income									(81)	(71)
Reclassification out of Accumulated Other Comprehensive Income | Foreign exchange contracts | Gains and Losses on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales									1,381	(203)
Cost of sales									(1,758)	(20)
Reclassification out of Accumulated Other Comprehensive Income | Commodity contracts | Gains and Losses on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales									0	0
Cost of sales									$ 270	$ 115