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REGULATORY MATTERS - GAS (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Nov. 16, 2023 | Dec. 31, 2023 | Jun. 30, 2023 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2019
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Revenues |  |  |  | $ (25,253.0) | $ (29,279.0) | $ (23,113.0) |
Total operating expenses |  |  |  | 19,427.0 | $ 23,909.0 | $ 19,415.0 |
Nicor Gas |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Infrastructure disallowed |  | $ 69.0 |  |  |  |  |
Pretax charge to income |  | 58.0 | $ 38.0 | (96.0) |  |  |
After tax charge to income |  | $ 44.0 | 28.0 | (72.0) |  |  |
Investing In Illinois Qualifying Infrastructure Plant | Nicor Gas |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Infrastructure disallowed | $ 126.8 |  |  | $ 63.0 |  |  | $ 32.0
Capital expenditures |  |  |  |  |  |  | $ 415.0
Revenues |  |  | 8.0 |  |  |  |
Total operating expenses |  |  | $ 30.0 |  |  |  |
QIP Rider | Nicor Gas |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Infrastructure disallowed | $ 31.0 |  |  |  |  |  |

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