Goodwill and other intangible assets - Summary of Other Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	$ 717,381	$ 632,844
Accumulated Amortization	(329,089)	(280,807)
Other Intangible Assets, Net	388,292	352,037
Patents
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	26,096	22,509
Accumulated Amortization	(11,669)	(9,539)
Customer lists
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	632,036	548,038
Accumulated Amortization	(287,831)	(246,946)
Trade names
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	32,427	31,174
Accumulated Amortization	(9,985)	(7,413)
Proprietary technology
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	24,525	28,748
Accumulated Amortization	(17,910)	(15,400)
Land use rights
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	172	282
Accumulated Amortization	(51)	(48)
Other
Other Intangible Assets, Gross:
Other Intangible Assets, Gross	2,125	2,093
Accumulated Amortization	$ (1,643)	$ (1,461)