Income taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Federal corporate tax rate	21.00%	35.00%
Provisional tax benefit	$ 17.9	$ 13.4
Provisional tax benefit, adjustment		4.5
Estimated undistributed foreign E&P		95.4
Provisional tax expense	13.3	13.6	$ 13.6
Provisional transition tax amount reduction		0.3
Deferred tax liabilities, net	50.5	54.1
Foreign NOLs	36.9	35.4
Federal losses carryforward	8.5	10.7
Valuation allowance	64.5	66.4
State losses carryforward	$ 17.4	$ 18.1
Effective income tax rate reconciliation, percent	30.00%	23.00%	30.00%
Unrecognized tax benefits, current	$ 0.0	$ 0.4
Unrecognized tax benefits, noncurrent	10.4	8.4
Gross unrecognized tax benefits	10.4	8.8	$ 2.0	$ 1.8
Unrecognized tax benefits acquired in business combinations	0.0	6.5
Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, amount	14.0
Tax credit carryforward, valuation allowance	9.1
Manitoba Scientific Research and Experimental Development
Income Tax Contingency [Line Items]
Tax credit carryforward, amount	11.0
Domestic Tax Authority
Income Tax Contingency [Line Items]
Deferred tax liabilities, net	7.7	4.8
Operating loss carryforwards	40.5
Federal losses carryforward	8.5
Valuation allowance	4.7
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Operating loss carryforwards	280.7
Valuation allowance	16.4
State losses carryforward	17.4
Operating loss carryforwards, valuation allowance	245.0
Foreign Tax Authority
Income Tax Contingency [Line Items]
Deferred tax liabilities, net	42.8
Deferred tax assets		$ 49.3
Operating loss carryforwards	199.0
Foreign NOLs	37.0
Valuation allowance	34.3
PaxVax
Income Tax Contingency [Line Items]
Unrecognized tax benefits acquired in business combinations	$ 7.0