Acquisitions (Details Textual) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Acquired in-process research and development	$ 27.5			$ 0.0	$ 112.5	$ 120.0
Karyopharm
Business Acquisition [Line Items]
Acquired in-process research and development			$ 10.0
Estimated additional payments upon achievement of milestones					207.0
Pfizer
Business Acquisition [Line Items]
Acquired in-process research and development		$ 75.0
Estimated additional payments upon achievement of milestones					515.0
TMS
Business Acquisition [Line Items]
Acquired in-process research and development					18.0
Estimated additional payments upon achievement of milestones					335.0
Research and development expense asset acquired		$ 4.0
AliveGen
Business Acquisition [Line Items]
Acquired in-process research and development	$ 27.5
Estimated additional payments upon achievement of milestones					535.0
Development Milestones | Pfizer
Business Acquisition [Line Items]
Estimated additional payments upon achievement of milestones					$ 10.0