Commitments and Contingencies - Pfizer License Agreement (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2015 USD ($)	Mar. 31, 2020 USD ($)
Commitments and Contingencies
Milestones or royalty payments triggered		$ 0
Termination fee		$ 3,000
Pfizer, Inc. | License Agreement
Commitments and Contingencies
Number of years after the first commercial sale	P5Y
Notice period	90 days
Pfizer, Inc. | License Agreement | Milestone Payments | Maximum
Commitments and Contingencies
Potential payments upon achievement of certain milestones	37,000