Acquisitions (Details Textual) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Business Acquisition [Line Items]
Acquired in-process research and development	$ 10.0	$ 0.0
Karyopharm
Business Acquisition [Line Items]
Acquired in-process research and development	10.0
Estimated additional payments upon achievement of milestones	$ 207.0

The amount of purchased research and development assets that are acquired in a business combination have no alternative future use and are therefore written off in the period of acquisition.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Name:	us-gaap_ResearchAndDevelopmentInProcess
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration