Rate Matters (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2026 |
Dec. 31, 2027 |
Dec. 31, 2025 |
Dec. 31, 2024 |
[3] | |||||||||||||||||
| Fuel Rules [Abstract] | |||||||||||||||||||||
| Deferred fuel rules monitored costs | $ 4.4 | [1] | $ 7.1 | [2] | $ 3.0 | ||||||||||||||||
| Electric Rate Proceeding [Member] | PSCW [Member] | MGE [Member] | |||||||||||||||||||||
| Rate Proceedings [Abstract] | |||||||||||||||||||||
| Proposed rate increase (decrease), percentage | [4],[5] | 0.15% | |||||||||||||||||||
| Proposed return on equity, percentage | 9.80% | ||||||||||||||||||||
| Proposed equity capital structure, percentage | 56.10% | ||||||||||||||||||||
| Authorized rate increase (decrease), percentage | [4],[6],[7] | 2.63% | |||||||||||||||||||
| Authorized return on equity, percentage | 9.70% | ||||||||||||||||||||
| Approved equity capital structure, percentage | 56.10% | ||||||||||||||||||||
| Fuel Rules [Abstract] | |||||||||||||||||||||
| Fuel rules, bandwidth | 2.00% | 2.00% | |||||||||||||||||||
| Electric Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member] | |||||||||||||||||||||
| Rate Proceedings [Abstract] | |||||||||||||||||||||
| Proposed rate increase (decrease), percentage | [4],[5] | 3.63% | |||||||||||||||||||
| Proposed return on equity, percentage | 9.80% | ||||||||||||||||||||
| Proposed equity capital structure, percentage | 56.10% | ||||||||||||||||||||
| Gas Rate Proceeding [Member] | PSCW [Member] | MGE [Member] | |||||||||||||||||||||
| Rate Proceedings [Abstract] | |||||||||||||||||||||
| Proposed rate increase (decrease), percentage | [4],[5] | 2.77% | |||||||||||||||||||
| Proposed return on equity, percentage | 9.80% | ||||||||||||||||||||
| Proposed equity capital structure, percentage | 56.10% | ||||||||||||||||||||
| Authorized rate increase (decrease), percentage | [4],[7] | 1.32% | |||||||||||||||||||
| Authorized return on equity, percentage | 9.70% | ||||||||||||||||||||
| Approved equity capital structure, percentage | 56.10% | ||||||||||||||||||||
| Gas Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member] | |||||||||||||||||||||
| Rate Proceedings [Abstract] | |||||||||||||||||||||
| Proposed rate increase (decrease), percentage | [4],[5] | 2.04% | |||||||||||||||||||
| Proposed return on equity, percentage | 9.80% | ||||||||||||||||||||
| Proposed equity capital structure, percentage | 56.10% | ||||||||||||||||||||
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