General form of registration statement for all companies including face-amount certificate companies

Long-term Debt - Silicon valley bank term loan (Details)

v3.21.2
Long-term Debt - Silicon valley bank term loan (Details)
6 Months Ended 12 Months Ended
Jul. 05, 2017
USD ($)
item
Jun. 30, 2021
M
shares
Dec. 31, 2020
USD ($)
$ / shares
shares
Dec. 31, 2019
USD ($)
shares
Mar. 31, 2020
USD ($)
$ / shares
shares
Feb. 12, 2019
$ / shares
shares
May 08, 2018
USD ($)
Debt Instrument [Line Items]              
Warrants to purchase shares of common stock | shares       3,386,246      
Evolv Technologies Holdings, Inc.              
Debt Instrument [Line Items]              
Number of monthly payments 36 36          
Warrants to purchase shares of common stock | shares   5,127,237 5,127,237   740,991    
Warrants exercise price | $ / shares         $ 0.15    
Evolv Technologies Holdings, Inc. | 2017 SVB Term Loan              
Debt Instrument [Line Items]              
Face amount of debt $ 5,000,000.0       $ 3,100,000    
Number of monthly payments | item 36            
Interest rate       5.25%      
Warrants to purchase shares of common stock | shares           75,000  
Warrants exercise price | $ / shares           $ 0.09  
Accrued interest, current       $ 100,000      
Interest expense       $ 200,000      
Evolv Technologies Holdings, Inc. | Term Loan A Advance              
Debt Instrument [Line Items]              
Face amount of debt $ 4,000,000.0            
Evolv Technologies Holdings, Inc. | Term Loan B Advance              
Debt Instrument [Line Items]              
Face amount of debt 1,000,000.0           $ 1,000,000.0
Evolv Technologies Holdings, Inc. | Revolving line of credit outstanding              
Debt Instrument [Line Items]              
Face amount of debt 1,000,000.0   $ 10,000,000.0   7,000,000.0    
Maximum borrowing capacity $ 1,000,000.0   $ 10,000,000.0   $ 7,000,000.0    
Interest rate     4.50%        
Evolv Technologies Holdings, Inc. | Wall Street Journal Prime Rate              
Debt Instrument [Line Items]              
Warrants to purchase shares of common stock | shares     1,000,000        
Warrants exercise price | $ / shares     $ 0.16        
Evolv Technologies Holdings, Inc. | Wall Street Journal Prime Rate | 2017 SVB Term Loan              
Debt Instrument [Line Items]              
Spread on variable rate 1.25%            
Interest rate 1.25%         5.25%  
Evolv Technologies Holdings, Inc. | Wall Street Journal Prime Rate | Revolving line of credit outstanding              
Debt Instrument [Line Items]              
Spread on variable rate     1.25%        
Interest rate     4.50%