v3.25.4
Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Feb. 27, 2026
Jun. 30, 2025
Cover Abstract      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Document Transition Report false    
Securities Act File Number 001-38905    
Entity Registrant Name NextCure, Inc.    
Entity Central Index Key 0001661059    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 47-5231247    
Entity Address, Address Line One 9000 Virginia Manor Road, Suite 200    
Entity Address, City or Town Beltsville    
Entity Address, State or Province MD    
Entity Address, Postal Zip Code 20705    
City Area Code 240    
Local Phone Number 399-4900    
Title of 12(b) Security Common Stock, $0.001 par value per share    
Trading Symbol NXTC    
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     $ 12.6
Entity Common Stock, Shares Outstanding   3,560,410  
Documents Incorporated by Reference [Text Block] Portions of the registrant’s definitive Proxy Statement for its 2026 Annual Meeting of Stockholders, which will be filed with the Commission within 120 days after December 31, 2025, are incorporated by reference into Part III of this Report.    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Auditor Name Ernst & Young LLP    
Auditor Firm ID 42    
Auditor Location Baltimore, Maryland