| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Income | | | | | | | | |
| Gain (loss) on trading of commodity futures contracts: | | | | | | | | |
| Realized gain (loss) on closed commodity futures contracts | 19.0 | 47.1 | 41.2 | 10.4 | -6.2 | 0.9 | 2.0 | -12.0 |
| |
| Change in unrealized gain (loss) on open commodity futures contracts | | | | | | | | |
| Dividend income | | | | | | | | |
| Interest income | 0.7 | 0.0 | 0.2 | 0.6 | 0.7 | 0.5 | 0.2 | 0.0 |
| ETF transaction fees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Total Income (Loss) | 28.4 | 49.1 | 43.0 | 13.6 | -11.1 | 0.7 | 5.7 | -8.6 |
| Total Income (Loss) growth | -42.2% | 14.2% | 215.6% | -222.5% | -1725.2% | -87.9% | -166.3% | -67.9% |
| Expenses | | | | | | | | |
| General Partner management fees | 0.6 | 0.6 | 0.4 | | | | | |
| Professional fees | 0.3 | 0.2 | 0.1 | 0.1 | 0.2 | 0.2 | 0.2 | 0.2 |
| Brokerage commissions | 0.1 | 0.1 | 0.1 | 0.0 | 0.0 | 0.1 | 0.1 | 0.1 |
| Directors' fees and insurance | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | | |
| License fees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Total Expenses | 20.3 | 48.3 | 42.1 | 10.9 | -5.5 | 1.7 | 3.0 | -11.0 |
| Net Income (Loss) | | | | | | | | |
| |
| Net Income (Loss) per limited partner share | $18.71 | $16.75 | ($8.02) | $9.57 | ($9.29) | $0.66 | $2.07 | ($4.60) |
| Net Income (Loss) per weighted average limited partner share | $14.97 | $16.85 | $11.14 | $10.69 | ($8.43) | $0.11 | $1.81 | ($3.88) |
| |
| Weighted average limited partner shares outstanding | 1.8 | 2.9 | 3.8 | 1.3 | 1.4 | 2.2 | 2.8 | 2.4 |