Business Combination, Asset Acquisitions, and Disposition - Acquisition of Alize Pharma II S.A.S. (Details) $ in Thousands, € in Millions	1 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($)	Mar. 31, 2016 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Acquired in-process research and development			$ 0	$ 85,000	$ 23,750
Alize Pharma II S.A.S | Upfront Payment
Business Acquisition [Line Items]
Acquired in-process research and development	$ 8,800
Alize Pharma II S.A.S | Milestone Payment
Business Acquisition [Line Items]
Potential payments under agreement for certain development, regulatory, and sales related milestones | €		€ 10