Commitment and Contingencies (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	May 31, 2019	Apr. 30, 2017	Feb. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Funding commitment, termination period				60 days
Research and development				$ 30,163	$ 20,346	$ 17,066
Sponsored Research Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum funding amount		$ 499
Funding commitment period		3 years
Research and development				166	$ 166	$ 111
Non-cancelable purchase commitments				55
Termination notice period	30 days
Maximum termination fees	$ 600
Adimab Option Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Option Fee			$ 250
Milestone payments			$ 25,000
Abbisko Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments receivable				$ 208,000