v3.24.0.1
Net Assets - Additional Information (Details) - USD ($)
 1 Months Ended 12 Months Ended 22 Months Ended 24 Months Ended
Nov. 02, 2023
Oct. 25, 2021
Dec. 01, 2017
Oct. 31, 2015
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Mar. 24, 2021
Dec. 31, 2023
Sep. 29, 2021
Feb. 24, 2022
Mar. 31, 2020
Class Of Stock [Line Items]                        
Common stock, shares authorized         100,000,000 100,000,000     100,000,000      
Common stock, par value         $ 0.01 $ 0.01     $ 0.01      
Proceeds from common stock issued             $ 119,294,000          
Issuance of common stock, value             119,294,000          
Stock repurchased during period, shares         0 871,345     0      
Stock repurchased during period, value           $ 10,800,000            
Dividends common stock         $ 73,322,000 $ 51,593,000 $ 44,943,000          
Stock issued during period, shares, dividend reinvestment plan         204,658 781,498 1,830,974          
Stock issued during period, value, dividend reinvestment plan         $ 2,500,000 $ 10,900,000 $ 26,995,000          
Maximum cost of shares that may be repurchased $ 25,000,000       $ 25,000,000       $ 25,000,000   $ 25,000,000  
Stock repurchase program, expiration date Nov. 02, 2024       Feb. 24, 2023              
Dividend Paid                        
Class Of Stock [Line Items]                        
Dividends common stock         $ 73,300,000              
Dividends Paid In Cash                        
Class Of Stock [Line Items]                        
Dividends common stock         70,800,000 40,700,000 17,900,000          
Dividend Declared                        
Class Of Stock [Line Items]                        
Dividends common stock         $ 73,300,000 $ 51,600,000 $ 44,900,000          
R. David Spreng                        
Class Of Stock [Line Items]                        
Issuance of common stock, Shares       1,667                
Issuance of common stock, value       $ 25,000                
Runway Growth Holdings LLC                        
Class Of Stock [Line Items]                        
Issuance of common stock, Shares               22,564        
Issuance of common stock, value               $ 300,000        
Offering price               $ 15       $ 15
IPO                        
Class Of Stock [Line Items]                        
Issuance of common stock, Shares   6,850,000                    
Offering price   $ 14.6                    
Proceeds from common stock issued   $ 93,000,000                    
Initial Private Offering                        
Class Of Stock [Line Items]                        
Issuance of common stock, Shares     18,241,157                  
Issuance of common stock, value     $ 275,000,000                  
Second Private Offering                        
Class Of Stock [Line Items]                        
Issuance of common stock, Shares                   9,617,379    
Issuance of common stock, value                   $ 144,300,000    
Capital commitments                   $ 181,700,000