Fair value measurement - Financial assets and liabilities carried at fair value measured on recurring basis (Details) - USD ($) $ in Thousands	Jun. 28, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Investments in marketable securities	$ 10,557	$ 10,926
Derivative assets	58,453	36,492
Derivative liabilities	3,578	1,387
Contingent consideration liabilities	49,279	219,908
Quoted prices in active markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Investments in marketable securities	10,557	10,926
Derivative assets	0	0
Derivative liabilities	0	0
Contingent consideration liabilities	0	0
Significant other observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Investments in marketable securities	0	0
Derivative assets	58,453	36,492
Derivative liabilities	3,578	1,387
Contingent consideration liabilities	0	0
Significant unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Investments in marketable securities	0	0
Derivative assets	0	0
Derivative liabilities	0	0
Contingent consideration liabilities	$ 49,279	$ 219,908