Income taxes, Net deferred tax asset (liability) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Net deferred tax asset (liability) [Abstract]
Federal losses carryforward	$ 10.7	$ 1.6
State losses carryforward	18.1	17.2
Research and development carryforward	10.1	3.5
State research and development carryforward	5.0	0.0
Scientific research and experimental development credit carryforward	13.1	16.5
Stock compensation	7.5	5.3
Foreign deferrals	35.4	34.1
Inventory reserves	3.4	1.6
Deferred revenue	11.6	0.0
Other	4.9	3.9
Deferred tax asset	119.8	83.7
Fixed assets	(46.4)	(23.1)
Intangible assets	(60.4)	(2.2)
Other	(0.7)	(10.5)
Deferred tax liability	(107.5)	(35.8)
Valuation allowance	(66.4)	(45.1)
Net deferred tax (liabilities)/ asset		$ 2.8
Deferred tax liabilities, net	$ (54.1)