Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 13, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2019
Entity Registrant Name	resTORbio, Inc.
Entity Central Index Key	0001720580
Trading Symbol	TORC
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38359
Entity Tax Identification Number	813305277
Entity Address, Address Line One	500 Boylston Street
Entity Address, Address Line Two	13th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
City Area Code	(857)
Local Phone Number	315-5521
Entity Common Stock, Shares Outstanding		36,221,660