Share-Based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	18.4	16.6	52.2	44.8
Related income tax (benefit) expense	(4.2)	(3.8)	(11.8)	(10.3)
Share-based compensation expense (benefit), net of taxes	14.2	12.8	40.4	34.5
Unrecognized compensation cost	108.4		$ 108.4
Recognition of share-based compensation expense (in years)			2 years 7 months 6 days
Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	3.8	2.4	$ 9.8	5.3
Related income tax (benefit) expense	(0.8)	(0.5)	(2.2)	(1.2)
Share-based compensation expense (benefit), net of taxes	3.0	1.9	7.6	4.1
Unrecognized compensation cost	28.4		$ 28.4
Recognition of share-based compensation expense (in years)			2 years 1 month 6 days
Cost of product sales | Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.3	0.2	$ 0.7	0.7
Cost of product sales | Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.3	0.1	0.8	0.3
Research and development | Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.9	0.9	2.7	2.8
Research and development | Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	1.3	0.5	3.2	1.1
Selling, general and administrative | Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	17.2	15.5	48.8	41.3
Selling, general and administrative | Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 2.2	$ 1.8	$ 5.8	$ 3.9