| In millions, except per share items | Jun-30-23 | Mar-31-23 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 | Jun-30-21 | Mar-31-21 |
| | 10-Q | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q |
| Revenues and other income | | | | | | | | |
| Revenues | | | | | | | | |
| Equity in earnings of Sisecam Wyoming | 27.0 | 19.3 | 14.6 | 14.8 | | | | |
| Total revenues and other income | 61.0 | 76.3 | 79.3 | 71.1 | 73.3 | 50.1 | 38.5 | 37.2 |
| Total revenues and other income growth | -23.1% | 7.3% | 106.0% | 91.3% | 118.6% | | | 9.5% |
| Operating expenses | | | | | | | | |
| Operating and maintenance expenses | 7.9 | 7.2 | 10.0 | 8.1 | | | | |
| Depreciation, depletion and amortization | 3.8 | 4.1 | 5.8 | 3.9 | 3.9 | 5.2 | 4.9 | 5.1 |
| General and administrative expenses | 5.6 | 5.8 | 5.1 | 4.5 | 5.8 | 4.1 | 3.4 | 4.1 |
| Asset impairments | 0.1 | | 0.0 | 0.0 | 1.0 | 0.1 | 0.0 | 4.0 |
| Total operating expenses | 17.4 | 17.1 | 21.0 | 16.4 | -33.7 | 45.0 | 18.6 | 47.6 |
| Income from operations | 73.8 | 82.1 | 79.0 | 73.3 | 65.2 | 39.2 | 25.1 | 18.4 |
| Operating margin | 121.0% | 107.7% | 99.5% | 103.1% | 89.0% | 78.2% | 65.1% | 49.4% |
| |
| Other expenses, net | | | | | | | | |
| Interest expense, net | -3.5 | -2.9 | -8.1 | -9.4 | -9.6 | -9.7 | -9.7 | -10.0 |
| Loss on extinguishment of debt | | | -4.0 | | | | | |
| Net income | 70.3 | 79.3 | 66.8 | 63.9 | 55.6 | 29.5 | 15.4 | 8.4 |
| Less: income attributable to preferred unitholders | -5.0 | -6.7 | -7.5 | -7.5 | -8.1 | -8.0 | -7.8 | -7.7 |
| Net income attributable to common unitholders and the general partner | 37.7 | 56.4 | 59.3 | 56.4 | 46.6 | 21.1 | 7.4 | 0.6 |
| Net income attributable to common unitholders | 37.7 | 56.4 | 59.3 | 56.4 | 46.6 | 21.1 | 7.4 | 0.6 |
| Net income attributable to the general partner | 0.8 | 1.1 | 1.2 | 1.1 | 1.0 | 0.4 | 0.2 | 0.0 |
| |
| Net income per common unit (see Note 5) | | | | | | | | |
| Basic (in dollars per share) | $2.93 | $4.40 | $4.65 | $4.45 | $3.78 | $1.71 | $0.60 | $0.05 |
| Diluted (in dollars per share) | $2.49 | $3.44 | $3.29 | $3.11 | $2.83 | $1.10 | $0.56 | $0.05 |
| Net income | 70.3 | 79.3 | 66.8 | 63.9 | 55.6 | 29.5 | 15.4 | 8.4 |
| |
| Comprehensive income (loss) from unconsolidated investment and other | | | | | | | | |
| Comprehensive income | | | | | | | | |