Janssen License and Collaboration Agreement - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 13, 2017	Dec. 31, 2017
Contract liabilities: Deferred revenue - related party
Deferred revenue - related party		$ 31,752
Collaborative Arrangement, Product
Contract liabilities: Deferred revenue - related party
License and collaboration revenue		20,100
Janssen biotech | Collaborative Arrangement, Product
Contract assets: Receivable from collaboration partner - related party
Additions		51,816
Deductions		(50,000)
Balance at end of period		1,816
Contract liabilities: Deferred revenue - related party
Additions		50,708
Deductions		(18,956)
Balance at end of period		31,752
Upfront cash payment	$ 50,000	50,000
Cost		700
License and collaboration revenue		19,000
Receivable from collaboration partner - related party		$ 1,800