Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2017	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Rent expense			$ 3,500,000	$ 2,000,000	$ 1,400,000
Milestone period			15 years
Envisia Therapeutics Inc.
Loss Contingencies [Line Items]
Milestone payments contingent upon the achievement of certain approvals (up to)	$ 45,000,000
Collaborative Arrangement
Loss Contingencies [Line Items]
Contingent payments due (up to)		$ 75,000,000