v3.25.1
Financial Highlights Per Share Performance - Summary of Per Share Data (Detail) - $ / shares
3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Investment Company, Financial Highlights [Roll Forward]        
Principal Market NAV, beginning of period $ 2.46 $ 0.8 $ 0.7 $ 0.68
Net (decrease) increase in net assets from investment operations:        
Net investment loss (0.01) (0.01) (0.02) (0.01)
Net realized and unrealized (loss) gain (1.7) 0.5 0.07 0.62
Net (decrease) increase in net assets resulting from operations (1.71) 0.49 0.05 0.61
Principal Market NAV, end of period $ 0.75 $ 1.29 $ 0.75 $ 1.29
Total return (69.51%) 61.25% 7.14% 89.71%
Ratios to average net assets:        
Net investment loss (2.50%) (2.50%) (2.50%) (2.50%)
Expenses (2.50%) (2.50%) (2.50%) (2.50%)