Collaborative Arrangements and Acquisitions - BioAxone Biosciences, Inc. (Details) - USD ($) $ in Thousands		6 Months Ended
	Oct. 01, 2014	Jun. 30, 2018	Dec. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent payments		$ 0	$ 0
BioAxone Biosciences Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred tax liability, intangible asset	$ 11,300
Collaborative arrangement, up-front payment	10,000	10,000
Maximum license fees and milestone payments	80,000
Contingent payments		$ 31,800	$ 18,900
In Process Research and Development | BioAxone Biosciences Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Acquired intangible asset	$ 29,000