| Consolidated Statement Of Operations (Unaudited) [Abstract] | |
| Operating Revenues | 515.88M |
| Cost Of Gas | 284.25M |
| Margin | 231.62M |
| Operating Expenses | |
| Operations and maintenance | 55.88M |
| Depreciation | 26.7M |
| General taxes | 9.53M |
| Utility income taxes | 53.3M |
| Total operating expenses | 145.41M |
| Operating Income (Loss) | 86.21M |
| Other Income (Expense) | |
| Income from equity method investments | 7.16M |
| Gain on sale of interest in equity method investment | |
| Non-operating income | 448K |
| Non-operating expense | -762K |
| Income taxes | |
| Total other income (expense) | 4.17M |
| Utility Interest Charges | |
| Interest on long-term debt | 12.68M |
| Allowance for borrowed funds used during construction | -8.31M |
| Other | 95K |
| Total utility interest charges | 4.46M |
| Net Income (Loss) | 85.92M |
| Average Shares Of Common Stock | |
| Basic | 72.36M |
| Diluted | 72.73M |
| Earnings (Loss) Per Share of Common Stock [Abstract] | |
| Basic | 1.19 |
| Diluted | 1.18 |
| Cash Dividends Per Share of Common Stock | 0.3 |