Annual report [Section 13 and 15(d), not S-K Item 405]

RELATED-PARTY TRANSACTIONS - Schedule of Management Fees, Incentive Fees and Associated Credits and Administration Fees (Details)

v3.25.4
RELATED-PARTY TRANSACTIONS - Schedule of Management Fees, Incentive Fees and Associated Credits and Administration Fees (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Administration fee      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities $ 2,617 $ 2,452 $ 2,255
Adviser      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities 8,007 8,370 10,374
Adviser | Base management fee      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities 8,007 8,370 8,603
Adviser | Incentive fee      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities 2,723 109 1,771
Adviser | Incentive fee waiver      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities (2,723) (109) 0
Gladstone Securities | Financing Fees and Selling Commissions and Dealer Management Fees      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities 16 41 583
Gladstone Securities | Selling Commissions and Dealer Management Fees      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities 1 41 583
Gladstone Securities | Financing Fees      
Related Party Transaction [Line Items]      
Total fees to Gladstone Securities $ 15 $ 0 $ 0