Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Jan. 31, 2022
Jun. 30, 2021
Document and Entity Information      
Auditor Name PricewaterhouseCoopers LLP    
Auditor Firm ID 238    
Auditor Location Boston, Massachusetts    
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2021    
Entity File Number 001-38586    
Entity Registrant Name RUBIUS THERAPEUTICS, INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 46-2688109    
Entity Address, Address Line One 399 Binney Street    
Entity Address, Address Line Two Suite 300    
Entity Address, City or Town Cambridge    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02139    
City Area Code 617    
Local Phone Number 679-9600    
Title of 12(b) Security Common Stock, par value $0.001 per share    
Trading Symbol RUBY    
Security Exchange Name NASDAQ    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
ICFR Auditor Attestation Flag true    
Entity Common Stock, Shares Outstanding   90,080,520  
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY    
Entity Central Index Key 0001709401    
Amendment Flag false    
Entity Well-known Seasoned Issuer No    
Entity Public Float     $ 851.6
Entity Voluntary Filers No