Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
9 Months Ended
Sep. 30, 2020
Nov. 04, 2020
Entity Registrant Name Hennessy Capital Acquisition Corp IV  
Entity Central Index Key 0001750153  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Document Type 10-Q  
Document Period End Date Sep. 30, 2020  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2020  
Entity Current Reporting Status Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Shell Company true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity File Number 001-37509  
Entity Interactive Data Current Yes  
Entity Incorporation State Country Code DE  
Class A Common Stock    
Entity Common Stock, Shares Outstanding   29,803,439
Class B Common Stock    
Entity Common Stock, Shares Outstanding   7,503,750