Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended
	Oct. 10, 2016	Mar. 31, 2020
Regeneron | Collaboration Agreement
Commitments and Contingencies
Payments made under the collaboration agreement		$ 0
Regeneron | Collaboration Agreement | Maximum
Commitments and Contingencies
Reimbursable clinical development costs	$ 25,000
Potential increase in reimbursable clinical development costs	$ 5,000
Incept
Commitments and Contingencies
Payments for Royalties		$ 341