Financial instruments - Fair value of derivatives (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Foreign Currency Exchange Contracts | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	$ 34,125	$ 0
Cash Flow Hedging
Derivatives Fair Value [Line Items]
Total asset derivatives	21,858	36,492
Total liability derivatives	35,995	1,387
Cash Flow Hedging | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	21,858	23,426
Cash Flow Hedging | Other assets
Derivatives Fair Value [Line Items]
Total asset derivatives	0	13,066
Cash Flow Hedging | Foreign Currency Exchange Contracts | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	1,870	1,387
Cash Flow Hedging | Foreign Currency Exchange Contracts | Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	1,691	1,659
Cash Flow Hedging | Foreign Currency Exchange Contracts | Designated as Hedging Instrument | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	1,504	1,285
Cash Flow Hedging | Foreign Currency Exchange Contracts | Not Designated as Hedging Instrument | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	61	192
Cash Flow Hedging | Foreign Currency Exchange Contracts | Not Designated as Hedging Instrument | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	366	102
Cash Flow Hedging | Cross Currency Interest Rate Contract | Prepaid expenses and other current assets
Derivatives Fair Value [Line Items]
Total asset derivatives	20,106	21,575
Cash Flow Hedging | Cross Currency Interest Rate Contract | Other assets
Derivatives Fair Value [Line Items]
Total asset derivatives	0	13,066
Cash Flow Hedging | Cross Currency Interest Rate Contract | Other liabilities
Derivatives Fair Value [Line Items]
Total liability derivatives	$ 34,125	$ 0