Asset Acquisitions and Contingent Consideration - Schedule of IPR&D Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development	$ 8,261	$ 2,000	$ 49,659
GB001
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development			19,148
GB004
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development			20,000
Other Programs
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development	761	1,000	3,011
GB1275
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development	$ 7,500	$ 1,000	$ 7,500