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Regulatory Matters - GAS Nicor Gas (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2019
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Total operating revenues | $ (5,748) | $ (7,206) | $ (12,228) | $ (13,854) |
Total operating expenses | 4,458 | $ 5,551 | $ 9,719 | $ 10,815 |
Nicor Gas |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Pre-tax charge to income | 38 |  |  |  |
After-tax charge to income | 28 |  |  |  |
Nicor Gas | Investing in Illinois |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Capital expenditures disallowed |  |  |  |  | $ 32
Capital expenditures |  |  |  |  | $ 415
Total operating revenues | 8 |  |  |  |
Total operating expenses | $ 30 |  |  |  |

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