XML 17 R1.htm IDEA: XBRL DOCUMENT v3.24.0.1
Cover - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Feb. 09, 2024
Jun. 30, 2023
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2023    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-36866    
Entity Registrant Name Summit Therapeutics Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 37-1979717    
Entity Address, Address Line One 601 Brickell Key Drive, Suite 1000    
Entity Address, City or Town Miami    
Entity Address, State or Province FL    
Entity Address, Postal Zip Code 33131    
City Area Code 650    
Local Phone Number 460-8308    
Title of 12(b) Security Common Stock, par value $0.01 per share    
Trading Symbol SMMT    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 108.4
Entity Common Stock, Shares Outstanding   701,697,179  
Amendment Flag false    
Entity Central Index Key 0001599298    
Document Fiscal Year Focus 2023    
Document Fiscal Period Focus FY