License and Asset Acquisitions - Schedule of IPR&D Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development	$ 3,600	$ 49,659	$ 5,500
GB002
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development			$ 5,500
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
GB1275
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development	1,000	7,501
Other Programs
Acquired Finite Lived Intangible Assets [Line Items]
Total in process research and development	$ 2,600	$ 3,010