Financial instruments - Fair values of derivative instruments designated as hedging instruments (Details) - Cash flow hedging - USD ($) $ in Thousands	Mar. 29, 2020	Dec. 31, 2019
Derivatives Fair Value [Line Items]
Total asset derivatives	$ 75,937	$ 36,492
Total liability derivatives	7,410	1,387
Other assets
Derivatives Fair Value [Line Items]
Total asset derivatives	45,347	13,066
Foreign exchange contract | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	30,590	23,426
Foreign exchange contract | Other current liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	7,410	1,387
Foreign exchange contract | Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	2,144	1,659
Foreign exchange contract | Designated as Hedging Instrument | Other current liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	6,030	1,285
Foreign exchange contract | Not Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	1,682	192
Foreign exchange contract | Not Designated as Hedging Instrument | Other current liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	1,380	102
Cross-currency interest rate swaps | Not Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	26,764	21,575
Cross-currency interest rate swaps | Not Designated as Hedging Instrument | Other assets
Derivatives Fair Value [Line Items]
Total asset derivatives	$ 45,347	$ 13,066