Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2019
Mar. 11, 2020
Jun. 28, 2019
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-K    
Document Period End Date Dec. 31, 2019    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2019    
Entity Current Reporting Status Yes    
Entity Filer Category Non-accelerated Filer    
Entity Ex Transition Period false    
Entity Small Business true    
Entity Shell Company true    
Entity Emerging Growth Company true    
Entity Well-known seasoned issuer No    
Entity Voluntary Filers No    
Entity Public Float     $ 297,148,500
Entity File Number 001-38821    
Entity Interactive Data Current Yes    
Entity Incorporation State Country Code DE    
Class A Common Stock      
Entity Common Stock, Shares Outstanding   22,060,109  
Class B Common Stock      
Entity Common Stock, Shares Outstanding   7,503,750