Income taxes, Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income tax reconciliation [Abstract]
US	$ 71.0	$ 80.7	$ 63.3
International	10.5	37.9	35.9
Earnings before taxes on income	81.5	118.6	99.2
Federal tax at statutory rates	17.1	41.5	34.7
State taxes, net of federal benefit	4.3	1.3	0.5
Impact of foreign operations	2.8	(2.2)	(9.9)
Change in valuation allowance	(0.1)	0.3	10.5
Tax credits	(1.8)	(1.9)	(1.6)
Transition Tax	(0.2)	13.6	0.0
Change in U.S. Tax Rate	(4.5)	(13.4)	0.0
Stock Compensation	(5.8)	(4.0)	0.0
Other differences	(0.9)	0.4	(0.6)
Return to provision true-ups	1.1	(0.5)	1.7
Transaction costs	5.4	0.0	0.0
GILTI, net	0.4	0.0	0.0
Permanent differences	1.0	0.9	1.4
Total provision for income taxes	$ 18.8	$ 36.0	$ 36.7
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective annual tax rate	23.00%	30.00%	37.00%
Provisional tax benefit	$ (17.9)	$ (13.4)
Provisional tax expense	$ 13.4	$ 13.6
Federal corporate tax rate	21.00%	35.00%