Share-Based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 29.2	$ (101.1)
Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	15.7	12.7
Related income tax benefit	(3.5)	(2.9)
Share-based compensation (benefit) expense, net of tax	12.2	9.8
Unrecognized compensation cost	$ 143.4
Recognition of share-based compensation expense (in years)	2 years 9 months 18 days
Restricted Stock Units
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 2.2	0.9
Restricted Stock Units \| 2015 Plan
Share-based compensation expense
Share-based compensation expense (benefit) before tax	2.2	0.9
Related income tax benefit	(0.5)	(0.2)
Share-based compensation (benefit) expense, net of tax	1.7	0.7
Unrecognized compensation cost	$ 35.6
Recognition of share-based compensation expense (in years)	2 years 7 months 6 days
Cost of product sales \| Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 0.2	0.3
Cost of product sales \| Restricted Stock Units \| 2015 Plan
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.2
Research and development \| Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.9	0.9
Research and development \| Restricted Stock Units \| 2015 Plan
Share-based compensation expense
Share-based compensation expense (benefit) before tax	0.7	0.1
Selling, general and administrative \| Stock Options
Share-based compensation expense
Share-based compensation expense (benefit) before tax	14.6	11.5
Selling, general and administrative \| Restricted Stock Units \| 2015 Plan
Share-based compensation expense
Share-based compensation expense (benefit) before tax	$ 1.3	$ 0.8

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The amount of expense, net of income tax, recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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