v3.26.3
Financial Highlights (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Feb. 10, 2026
Oct. 30, 2020
Sep. 30, 2026
Sep. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Investment Company, Financial Highlights [Roll Forward]            
Net asset value per common share at beginning of year (in dollars per share)     $ 5.71 $ 6.56 $ 6.56  
Net investment income (in dollars per share)     0.15 0.17    
Net realized and change in unrealized gains (losses) (in dollars per share)     (0.20) (0.01)    
Net increase (decrease) from operations (in dollars per share)     (0.05) 0.16    
Net increase (decrease) from operations applicable to common stockholders (in dollars per share)     (0.10) 0.10    
Effect of other comprehensive income (in dollars per share)     0 0    
Common stock transactions (in dollars per share)     (0.15) (0.08)    
Net asset value per common share at end of year (in dollars per share)     5.36 6.45 $ 5.71 $ 6.56
Per share market value at end of year (in dollars per share)     $ 2.08 $ 2.75    
Total return based on market value     (5.36%) (9.34%)    
Total return based on net asset value     (1.33%) 3.08%    
Shares of common stock outstanding at end of year (in shares)     536,295,785 465,916,352 512,746,556  
Weighted average shares of common stock outstanding (in shares)     524,466,279 461,356,032    
Ratios/Supplemental Data            
Net assets at end of year     $ 2,875,089 $ 3,004,790 $ 2,928,846 $ 2,988,772
Portfolio turnover rate     1.47% 1.39%    
Annualized ratio of operating expenses to average net assets applicable to common shares     10.39% 10.45%    
Annualized ratio of net investment income to average net assets applicable to common shares     10.53% 10.59%    
Ratio of operating expenses to average net assets applicable to common shares     10.84%      
5.50% Preferred Stock            
Ratios/Supplemental Data            
Dividend rate 5.50% 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% 6.50%
2030 Notes            
Ratios/Supplemental Data            
Dividend rate     5.50%      
Preferred Stock            
Investment Company, Financial Highlights [Roll Forward]            
Distributions of net investment income (in dollars per share)     $ (0.05) $ (0.06)    
Total distributions (in dollars per share)     (0.05) (0.06)    
Common Stock            
Investment Company, Financial Highlights [Roll Forward]            
Distributions of net investment income (in dollars per share)     (0.11) (0.12)    
Total distributions (in dollars per share)     (0.11) (0.14)    
Return of Capital to common stockholders (in dollars per share)     $ 0 $ (0.02)    
Shares of common stock outstanding at end of year (in shares)     536,295,785 465,916,352 512,746,556 455,902,826
Ratios/Supplemental Data            
Net assets at end of year     $ 536 $ 466 $ 513 $ 456