Components of Exchange Gas Receivable (Detail) - USD ($) $ in Millions |
Jun. 30, 2025 |
Dec. 31, 2024 |
Jun. 30, 2024 |
|---|---|---|---|
| Receivables [Line Items] | |||
| Total Exchange Gas Receivable | $ 9.1 | $ 6.4 | $ 5.8 |
| Northern Utilities Inc | |||
| Receivables [Line Items] | |||
| Total Exchange Gas Receivable | 7.8 | 6.0 | 5.4 |
| Fitchburg | |||
| Receivables [Line Items] | |||
| Total Exchange Gas Receivable | 0.4 | $ 0.4 | $ 0.4 |
| Bangor | |||
| Receivables [Line Items] | |||
| Total Exchange Gas Receivable | $ 0.9 |