License Funding and Other Agreements Related to the CVR - Additional Information (Details) - USD ($) $ in Millions		1 Months Ended		12 Months Ended
	Oct. 31, 2020	Nov. 30, 2020	May 31, 2019	Dec. 31, 2020	Mar. 23, 2017
Research And Development Arrangement Contract To Perform For Others [Line Items]
Increase decrease in estimated fair value of CVR liability				$ 1.9
Estimated fair value of the CVR liability				1.0
National Institute of Health
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant term			5 years
Grants receivable			$ 1.5
Qualifying expenses				0.6
National Institute of Health | Research Funding Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Qualifying expenses				0.7
Contingent Value Rights Agreement | C O V I D19
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total fees and expenses related to clinical trials	$ 1.1			$ 3.0
Increase decrease in estimated fair value of CVR liability		$ 1.9
Estimated fair value of the CVR liability		$ 1.0
Novartis License Agreement | Novartis International Pharmaceutical Ltd.
Research And Development Arrangement Contract To Perform For Others [Line Items]
License agreement termination description				The agreement may be terminated by either party upon a material breach of obligation by the other party that is not cured with 60 days after written notice. resTORbio may terminate the agreement in its entirety or on a product-by-product or country-by-country basis with or without cause with 60 days’ prior written notice.
Novartis License Agreement | Novartis International Pharmaceutical Ltd. | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Aggregate amount payable upon satisfaction of clinical milestones					$ 4.3
Aggregate amount payable upon satisfaction of regulatory milestones for first indication approved					24.0
Aggregate amount payable upon satisfaction of regulatory milestones for second indication approved					18.0
Aggregate amount payable upon satisfaction of commercial milestones					$ 125.0