v3.26.1
Financial Highlights (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Feb. 10, 2026
Oct. 30, 2020
Aug. 03, 2020
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2022
Investment Company, Financial Highlights [Roll Forward]                
Net asset value per common share at beginning of year (in dollars per share)       $ 6.56 $ 8.74 $ 9.24 $ 10.48 $ 9.81
Net investment income (in dollars per share)       0.68 0.77 1.02 1.06 0.88
Net realized and change in unrealized gains (losses) (in dollars per share)       (0.40) (1.87) (0.42) (1.31) 0.61
Net increase (decrease) from operations (in dollars per share)       0.28 (1.11) 0.60 (0.25) 1.49
Net increase (decrease) from operations applicable to common stockholders (in dollars per share)       0.06 (1.35) 0.36 (0.43) 1.43
Common stock transactions (in dollars per share)       (0.41) (0.25) (0.15) (0.10) (0.05)
Offering costs from issuance of preferred stock (in dollars per share)       0 0 0 0 (0.03)
Reclassification of preferred stock issuance costs (in dollars per share)       0 0 0 0 0.03
Net asset value per common share at end of year (in dollars per share)       5.71 6.56 8.74 9.24 10.48
Per share market value at end of year (in dollars per share)       $ 2.31 $ 3.18 $ 5.53 $ 6.20 $ 6.99
Total return based on market value       (10.73%) (33.71%) 1.47% (1.37%) (8.59%)
Total return based on net asset value       6.97% (13.47%) 7.61% (1.96%) 17.21%
Shares of common stock outstanding at end of year (in shares)       512,746,556 455,902,826 424,846,963 404,033,549 393,164,437
Weighted average shares of common stock outstanding (in shares)       479,866,265 440,314,909 412,703,365 398,514,965 390,571,648
Ratios/Supplemental Data                
Net assets at end of year       $ 2,928,846 $ 2,988,772 $ 3,711,733 $ 3,732,665 $ 4,119,123
Portfolio turnover rate       7.03% 12.43% 7.56% 6.05% 15.92%
Ratio of operating expenses to average net assets applicable to common shares       10.55% 11.26% 11.84% 11.01% 9.00%
Ratio of net investment income to average net assets applicable to common shares       11.00% 10.03% 11.25% 10.75% 8.44%
Ratio of operating expenses to average net assets applicable to common shares       11.13%        
5.50% Preferred Stock                
Ratios/Supplemental Data                
Dividend rate 5.50% 5.50% 5.50% 5.50% 5.50%      
6.50% Preferred Stock                
Ratios/Supplemental Data                
Dividend rate     6.50% 6.50% 6.50%      
Preferred Stock                
Investment Company, Financial Highlights [Roll Forward]                
Distributions of net investment income (in dollars per share)       $ (0.22) $ (0.24) $ (0.24) $ (0.17) $ (0.05)
Distributions of capital gains to preferred stockholders (in dollars per share)       0 0 0 0 (0.01)
Total distributions (in dollars per share)       (0.22) (0.24) (0.24) (0.17) (0.06)
Common Stock                
Investment Company, Financial Highlights [Roll Forward]                
Distributions of net investment income (in dollars per share)       (0.50) (0.44) (0.56) (0.60) (0.60)
Distributions of capital gains to preferred stockholders (in dollars per share)       0 0 0 (0.02) (0.11)
Total distributions (in dollars per share)       (0.52) (0.60) (0.72) (0.72) (0.72)
Return of Capital to common stockholders (in dollars per share)       (0.02) (0.16) (0.16) (0.10) (0.01)
Effect of other comprehensive income (in dollars per share)       $ 0.01
Shares of common stock outstanding at end of year (in shares)       512,746,556 455,902,826 424,846,963 404,033,549  
Ratios/Supplemental Data                
Net assets at end of year       $ 513 $ 456 $ 425 $ 404