| In millions, except per share items | Sep-30-21 | Jun-30-21 | Mar-31-21 | Dec-31-20 | Sep-30-20 | Jun-30-20 | Mar-31-20 | Dec-31-19 |
| | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K |
| REVENUES: | | | | | | | | |
| Revenues | 58.7 | 38.1 | 31.9 | 28.9 | 21.5 | 20.5 | 23.0 | 30.2 |
| Revenues growth | 173.6% | 86.1% | 38.7% | -4.2% | -21.0% | -35.8% | -21.1% | -11.0% |
| OPERATING EXPENSES: | | | | | | | | |
| Lease operating expense | 3.3 | 4.0 | 3.2 | 3.6 | 2.8 | 3.2 | 3.3 | 3.5 |
| Production and other taxes | 1.3 | 0.8 | 0.6 | 0.4 | 0.6 | 0.9 | 0.9 | 0.7 |
| Transportation and processing | 4.8 | 4.6 | 4.0 | 4.5 | 4.3 | 5.4 | 4.9 | 5.1 |
| Depreciation, depletion and amortization | 13.4 | 12.2 | 10.1 | 11.1 | 10.3 | 11.9 | 13.3 | 14.2 |
| General and administrative | 4.3 | 3.4 | 3.5 | 4.7 | 3.9 | 4.5 | 4.9 | 5.3 |
| Impairment of oil and natural gas properties | | | | 19.8 | 3.0 | 14.1 | | |
| Other | 0.0 | 0.0 | -0.2 | 0.0 | 0.0 | 0.0 | 0.0 | -0.1 |
| Operating Expenses, Total | 27.1 | 25.1 | 21.2 | 44.1 | 25.0 | 40.0 | 27.3 | 28.7 |
| Operating income (loss) | 31.6 | 13.0 | 10.6 | -15.2 | -3.6 | -19.6 | -4.3 | 1.4 |
| Operating margin | 53.9% | 34.2% | 33.3% | -52.7% | -16.6% | -95.5% | -18.6% | 4.7% |
| |
| OTHER INCOME (EXPENSE): | | | | | | | | |
| Interest expense | -2.2 | -2.1 | -1.9 | -1.6 | -1.7 | -1.7 | -2.0 | -2.0 |
| Interest income and other expense | -79.6 | -24.6 | -6.1 | 15.3 | -25.6 | -6.8 | 14.6 | -6.9 |
| Loss on commodity derivatives not designated as hedges | -77.4 | -22.5 | -3.3 | 8.0 | -11.1 | -1.7 | 9.1 | -0.4 |
| Loss on early extinguishment of debt | | | -0.9 | | | | | |
| Nonoperating Income (Expense), Total | -79.6 | -24.6 | -6.1 | 6.4 | -12.8 | -3.4 | 7.3 | -2.4 |
| Loss before income taxes | -48.0 | -11.6 | 4.5 | -8.8 | -16.4 | -22.9 | 3.0 | -0.9 |
| Income tax expense | | | | | | | | |
| Net loss | -48.0 | -11.6 | 4.5 | -8.8 | -16.4 | -22.9 | 3.0 | -0.9 |
| |
| PER COMMON SHARE | | | | | | | | |
| Net loss per common share - basic (in dollars per share) | ($3.52) | ($0.86) | $0.34 | ($0.69) | ($1.30) | ($1.83) | $0.24 | ($0.07) |
| Net loss per common share - diluted (in dollars per share) | ($3.52) | ($0.86) | $0.30 | ($0.69) | ($1.30) | ($1.83) | $0.22 | ($0.06) |
| |
| Weighted average shares of common stock outstanding - basic (in shares) | 13.6 | 13.4 | 13.4 | 12.6 | 12.6 | 12.5 | 12.5 | 12.2 |
| Weighted average shares of common stock outstanding - diluted (in shares) | 13.6 | 13.4 | 14.8 | 12.6 | 12.6 | 12.5 | 13.8 | 13.9 |