Collaboration and License Revenue - Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Contract liabilities:
Deferred revenue, Balance at Beginning of Period	$ 33,558
Deferred revenue, Deductions	$ (33,558)	$ (11,442)
Deferred revenue, Balance at End of Period		$ 33,558