Collaboration Agreements - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Contract liabilities
Deferred revenue, Balance at Beginning of Period	$ 4,815	$ 46,196
Deferred revenue, Deductions	11	40,592
Deferred revenue, Balance at End of Period	4,804	5,604
Revenue recognized in the period from:
Amounts included in the contract liability at the beginning of the period	$ 11	$ 40,592