v3.19.3
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 08, 2019
[DocumentAndEntityInformationAbstract]    
Entity Registrant Name NextCure, Inc.  
Entity Central Index Key 0001661059  
Document Type 10-Q  
Document Period End Date Sep. 30, 2019  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Non-accelerated Filer  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   22,753,960