Integration and acquisition costs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Business Acquisition [Line Items]
Integration and acquisition costs	$ 6.6	$ 4.1
Change in fair value of contingent consideration	(59.2)
Viropharma
Business Acquisition [Line Items]
Integration and acquisition costs	65.8	0
Acquisition and Integration Costs, Gross Amount | FerroKin
Business Acquisition [Line Items]
Change in fair value of contingent consideration	(71.9)
Acquisition and Integration Costs, Gross Amount | Viropharma
Business Acquisition [Line Items]
Integration and acquisition costs	65.8
Acquisition and Integration Costs, Net Amount
Business Acquisition [Line Items]
Integration and acquisition costs	$ 6.6