Income taxes - Reconciliation items from U.S. statutory income tax rate to the effective tax rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. statutory income tax rate	21.00%	21.00%	35.00%
U.S. tax benefit for foreign derived intangible income	(4.90%)	(5.30%)	0.00%
U.S. excess tax benefit for stock compensation	(3.10%)	(2.00%)	(4.10%)
U.S. R&D tax credit	(1.40%)	(1.30%)	(1.10%)
Non-U.S. effective tax rates	0.30%	0.10%	(2.50%)
U.S. Tax Act transitional non-cash expense	0.00%	4.20%	0.00%
U.S. Tax Act enactment-date effects and measurement period adjustments	0.00%	(0.70%)	12.70%
U.S. tax benefit for manufacturing	0.00%	0.00%	(1.60%)
Other	0.50%	0.50%	1.00%
Effective tax rate	12.40%	16.50%	39.40%