Celgene Collaboration Agreement - Performance Obligations (Details) - Celegene Collaborative Arrangement - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01	Dec. 31, 2018
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period for unit of accounting	12 months
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period for unit of accounting	4 years