Goodwill and intangible assets - Schedule of intangible assets subject to amortization (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Dec. 31, 2019
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance	$ 900,937
Intangible assets recognized during the period	12,789
Currency translation during the period	(11,062)
Intangible assets subject to amortization, ending balance	902,664
Accumulated amortization, beginning balance	674,790
Amortization during the period	6,876	$ 6,729
Currency translation during the period	(4,122)
Accumulated amortization, ending balance	677,544
Intangible assets subject to amortization, net	225,120		$ 226,147
Customer relationships
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance	645,206
Intangible assets recognized during the period	12,789
Currency translation during the period	(9,387)
Intangible assets subject to amortization, ending balance	648,608
Accumulated amortization, beginning balance	426,765
Amortization during the period	6,324
Currency translation during the period	(2,670)
Accumulated amortization, ending balance	430,419
Intangible assets subject to amortization, net	218,189
Patents
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance	249,100
Intangible assets recognized during the period	0
Currency translation during the period	(1,471)
Intangible assets subject to amortization, ending balance	247,629
Accumulated amortization, beginning balance	246,872
Amortization during the period	510
Currency translation during the period	(1,445)
Accumulated amortization, ending balance	245,937
Intangible assets subject to amortization, net	1,692
Other
Finite-lived Intangible Assets [Roll Forward]
Intangible assets subject to amortization, beginning balance	6,631
Intangible assets recognized during the period	0
Currency translation during the period	(204)
Intangible assets subject to amortization, ending balance	6,427
Accumulated amortization, beginning balance	1,153
Amortization during the period	42
Currency translation during the period	(7)
Accumulated amortization, ending balance	1,188
Intangible assets subject to amortization, net	$ 5,239