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Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Oct. 31, 2022 | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2022 | Sep. 30, 2021 | Apr. 06, 2022
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Regulatory Deferral - Joint Venture |  | $ (2.2) | $ 0.0 | $ (4.5) | $ 0.0 |
Minimum |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Recommended Rate increase, percentage |  |  |  |  |  | 4.00%
Recommended Rate Increase, Amount |  |  |  |  |  | $ 35.2
Maximum |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Recommended Rate increase, percentage |  |  |  |  |  | 6.30%
Recommended Rate Increase, Amount |  |  |  |  |  | $ 57.6
Columbia Of Ohio |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Percentage |  |  |  | 21.30% |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ 221.4 |  |
Columbia Of Ohio | Subsequent Event |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Percentage | 7.97% |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount | $ 68.2 |  |  |  |  |
NIPSCO - Electric | Overrecovered Gas and Fuel Costs |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |
Regulatory Liabilities |  | $ 8.0 |  | $ 8.0 |  |

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