Quarterly report [Sections 13 or 15(d)]

SHARE-BASED COMPENSATION - Narrative (Details)

v3.25.1
SHARE-BASED COMPENSATION - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]    
Share‑based compensation $ 4,842 $ 4,103
Restricted Stock    
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]    
Share‑based compensation 4,800 $ 4,100
Share-based payment arrangement, nonvested award, excluding option, cost not yet recognized, amount $ 26,100  
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition (in years) 2 years 4 months 24 days  
Restricted Stock | Minimum    
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]    
Vesting period (in years) 3 years  
Restricted Stock | Maximum    
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]    
Vesting period (in years) 5 years  
Restricted Stock | Main Street Capital Corporation 2022 Equity and Incentive Plan | Minimum    
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]    
Vesting period (in years) 3 years  
Restricted Stock | Main Street Capital Corporation 2022 Equity and Incentive Plan | Maximum    
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]    
Vesting period (in years) 5 years