Collaboration Agreements - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Contract liabilities
Deferred revenue, Balance at Beginning of Period			$ 46,196	$ 52,439
Deferred revenue, Additions				2,373
Deferred revenue, Deductions			41,550	7,906
Deferred revenue, Balance at End of Period	$ 4,646	$ 46,906	4,646	46,906
Revenue recognized in the period from:
Amounts included in the contract liability at the beginning of the period	$ 834	$ 1,760	$ 41,550	$ 7,515