Share-Based Compensation - Share Tracking Awards Plans - Benefit recognized (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 benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	$ 23.9	$ 51.4	$ 15.9	$ (29.2)
STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	1.4	32.2	(47.0)	(80.1)
Related income tax (benefit) expense	(0.2)	(7.4)	10.7	18.3
Share-based compensation expense (benefit), net of taxes	1.2	24.8	(36.3)	(61.8)
Cash payments on awards exercised during the period			6.9	71.5
Cost of product sales \| STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	0.1	2.0	(1.9)	(4.0)
Research and development \| STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	0.4	6.8	(9.9)	(15.2)
Selling, general and administrative \| STAP awards
Share based compensation benefit recognized in connection with the STAP
Share-based compensation expense (benefit) before tax	$ 0.9	$ 23.4	$ (35.2)	$ (60.9)

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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