| In millions, except per share items | Jun-30-23 | Mar-31-23 | Dec-31-22 | Sep-30-22 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 |
| | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q |
| Operating Revenues | | | | | | | | |
| Regulated Energy | 101.1 | 142.3 | 118.4 | 91.0 | 92.2 | 127.9 | 101.4 | 80.4 |
| Unregulated Energy and other | 34.5 | 75.9 | | | 47.3 | 95.0 | | |
| Total Operating Revenues | 135.6 | 218.1 | 187.3 | 131.1 | 139.5 | 222.9 | 160.4 | 107.3 |
| Total Operating Revenues growth | -2.8% | -2.1% | 16.8% | 22.1% | 25.6% | 16.6% | 17.0% | 5.8% |
| Operating Expenses | | | | | | | | |
| Natural gas and electric costs | 23.9 | 55.3 | | | 21.6 | 45.4 | | |
| Propane and natural gas costs | 11.9 | 33.3 | | | 25.5 | 51.7 | | |
| Operations | 42.2 | 44.8 | 43.5 | 40.2 | 38.0 | 42.8 | 38.4 | 34.1 |
| |
| Settlement Gain | | | | | | | | |
| Depreciation and amortization | 17.3 | 17.2 | 17.4 | 17.3 | 17.2 | 17.0 | 16.2 | 15.8 |
| Other taxes | 6.7 | 7.6 | 6.5 | 6.2 | 6.2 | 6.8 | 6.1 | 5.7 |
| Total Operating Expenses | 107.2 | 163.2 | 144.3 | 112.4 | 113.0 | 168.0 | 123.5 | 87.2 |
| Total operating income | 28.3 | 54.9 | 43.0 | 18.6 | 26.5 | 54.9 | 36.8 | 20.1 |
| Operating margin | 20.9% | 25.2% | 22.9% | 14.2% | 19.0% | 24.6% | 23.0% | 18.7% |
| Other income, net | 0.8 | 0.3 | 0.6 | 1.0 | 2.6 | 0.9 | -0.4 | 0.3 |
| Interest charges | -7.0 | -7.2 | -7.0 | -6.2 | -5.8 | -5.3 | -5.0 | -5.0 |
| Income Before Income Taxes | 22.2 | 48.0 | 36.6 | 13.4 | 23.2 | 50.4 | 31.4 | 15.5 |
| Income Taxes | 6.1 | 11.6 | 10.4 | 3.7 | 6.2 | 13.5 | 8.7 | 3.0 |
| Tax rate | 27.4% | 24.2% | 28.5% | 27.7% | 26.6% | 26.8% | 27.6% | 19.3% |
| |
| Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax | | | | | | | | |
| Net Income | 16.1 | 36.3 | 26.2 | 9.7 | 17.1 | 36.9 | 22.7 | 12.5 |
| |
| Weighted Average Common Shares Outstanding: | | | | | | | | |
| Basic (shares) | 17.8 | 17.8 | 17.7 | 17.7 | 17.7 | 17.7 | 17.6 | 17.6 |
| Diluted (shares) | 17.9 | 17.8 | 17.8 | 17.8 | 17.8 | 17.8 | 17.6 | 17.7 |
| |
| Earnings Per Share of Common Stock: | | | | | | | | |
| Income (Loss) from Continuing Operations, Per Basic Share | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| |
| Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share | | | | | | | | |
| Basic (in dollars per share) | $0.91 | $2.05 | $1.48 | $0.54 | $0.96 | $2.09 | $1.29 | $0.71 |
| |
| Earnings Per Share, Diluted [Abstract] | | | | | | | | |
| Income (Loss) from Continuing Operations, Per Diluted Share | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| |
| Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share | | | | | | | | |
| Diluted (in dollars per share) | $0.90 | $2.04 | $1.46 | $0.54 | $0.96 | $2.08 | $1.28 | $0.71 |