Related Party Transactions - Additional Information (Details) $ in Thousands		12 Months Ended
	Jun. 11, 2018 Investor	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Related Party Transaction [Line Items]
Net product sales		$ 344,775
Royalty Transfer Agreement
Related Party Transaction [Line Items]
Royalty owed to charitable foundation		$ 0	$ 0
Royalty Transfer Agreement | MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation
Related Party Transaction [Line Items]
Number of investors | Investor	2
Obligation to pay royalties		royalty equal to 1% of its net product sales on any product developed or owned by iTeos Therapeutics, Inc. or iTeos Belgium S.A., each year within 120 days following each year end.
Percentage of royalty required to pay	1.00%
Royalty Transfer Agreement | Product
Related Party Transaction [Line Items]
Net product sales		$ 0	$ 0