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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 |

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- Definition 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. + References 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 + Details
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