| 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 |
| Gain (loss) on trading of commodity futures contracts: | | | | | | | | |
| Realized gain (loss) on closed commodity futures contracts | 79.0 | 150.1 | 119.9 | 18.2 | -4.2 | 12.3 | 27.9 | -41.8 |
| |
| Change in unrealized gain (loss) on open commodity futures contracts | | | | | | | | |
| Dividend income | | | | | | | | |
| Interest income | 1.7 | 0.1 | 0.4 | 1.4 | 1.3 | 0.7 | 0.3 | 0.1 |
| ETF transaction fees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Total Income (Loss) | 85.2 | 160.5 | 121.7 | 27.6 | -14.3 | 16.4 | 38.0 | -42.8 |
| |
| Expenses | | | | | | | | |
| General Partner management fees | 2.0 | 2.3 | 2.2 | | | | | |
| Professional fees | 0.2 | 0.4 | 0.3 | 0.1 | 0.1 | 0.3 | 0.2 | 0.1 |
| Brokerage commissions | 0.2 | 0.3 | 0.5 | 0.1 | 0.1 | 0.1 | 0.2 | 0.1 |
| Directors' fees and insurance | 0.1 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Registration fees | 0.2 | 0.3 | 0.2 | | | | | |
| Total Expenses | 79.3 | 150.5 | 120.2 | 19.1 | 3.1 | 13.8 | 29.2 | 40.7 |
| Net Income (Loss) | 82.6 | 157.5 | 119.1 | 26.8 | -15.2 | 15.5 | 37.0 | -43.6 |
| |
| Net Income (Loss) per limited partner share | $7.39 | $7.96 | ($8.00) | $5.73 | ($3.00) | $2.48 | $3.48 | ($10.17) |
| Net Income (Loss) per weighted average limited partner share | $9.19 | $9.23 | $4.45 | $5.76 | ($3.14) | $2.24 | $4.49 | ($9.02) |
| |
| Weighted average limited partner shares outstanding | 9.0 | 17.1 | 26.8 | 4.6 | 4.8 | 6.9 | 8.2 | 4.8 |