Income taxes (Reconciliation of Federal Statutory Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory tax rate	21.00%	21.00%	35.00%
2017 Tax Act, net repatriation tax	0.00%	0.00%	70.70%
Foreign earnings	(4.50%)	(4.30%)	(15.80%)
2017 Tax Act, net deferred tax remeasurement	0.00%	0.00%	(6.90%)
Credits, Puerto Rico Excise Tax	(2.60%)	(2.50%)	(2.20%)
2017 Tax Act, net impact on intercompany sales	0.00%	(1.80%)	0.00%
Interest on uncertain tax positions	1.60%	1.20%	0.60%
Credits, primarily federal R&D	(1.00%)	(0.80%)	(0.60%)
Share-based payments	(0.30%)	(0.20%)	(0.70%)
Other, net	0.00%	(0.50%)	(0.70%)
Effective tax rate	14.20%	12.10%	79.40%