Financial instruments - Fair values of derivative instruments designated as hedging instruments (Details) - USD ($) $ in Thousands	Mar. 28, 2021	Dec. 31, 2020
Cash flow hedging
Derivatives Fair Value [Line Items]
Total asset derivatives	$ 26,885	$ 21,858
Total liability derivatives	13,976	35,995
Foreign exchange contract | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	12,054	34,125
Foreign exchange contract | Cash flow hedging | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	26,885	21,858
Foreign exchange contract | Cash flow hedging | Other current liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	1,922	1,870
Foreign exchange contract | Designated as Hedging Instrument | Cash flow hedging | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	1,098	1,691
Foreign exchange contract | Designated as Hedging Instrument | Cash flow hedging | Other current liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	1,706	1,504
Foreign exchange contract | Not Designated as Hedging Instrument | Cash flow hedging | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	212	61
Foreign exchange contract | Not Designated as Hedging Instrument | Cash flow hedging | Other current liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	216	366
Cross-currency interest rate swaps | Not Designated as Hedging Instrument | Cash flow hedging | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	25,575	20,106
Cross-currency interest rate swaps | Not Designated as Hedging Instrument | Cash flow hedging | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	$ 12,054	$ 34,125