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Related Party Transactions - Additional Information (Details)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 30, 2017 TargetAntigen	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Related Party Transaction [Line Items]
Rent expense incurred under operating lease		$ 42,000	$ 42,000	$ 84,000	$ 84,000
Surface Oncology, Inc.
Related Party Transaction [Line Items]
Number of target antigens against which antibodies are to be identified and selected \| TargetAntigen	2
Upfront payments fee received		$ 25,000	$ 64,000	$ 118,877	$ 133,000	$ 250,000