Agreements with Incyte Corporation - Deferred revenue liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Changes in deferred revenue liabilities:
Deferred revenue, Balance at Beginning of Period	$ 0
Deferred revenue, Additions	12,252
Deferred revenue, Deductions	745
Deferred revenue, Balance at End of Period	$ 11,507