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Regulatory Matters - Quarterly Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020
Public Utilities, General Disclosures [Line Items] |  |  |
Regulatory liabilities | $ 204 |  | $ 151
Operating Revenue | 2,083 | $ 1,864 |
Consumers Energy Company |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Regulatory liabilities | 204 |  | 151
Operating Revenue | 1,937 | $ 1,744 |
Consumers Energy Company | Energy Waste Reduction Plan Incentive |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Requested recovery/collection | 42 |  |
Operating Revenue |  |  | 42
Reserve for customer refunds | Consumers Energy Company |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Regulatory liabilities | 28 |  | 28
Gain shared with customers | Consumers Energy Company |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Regulatory liabilities | $ 14 |  | $ 14

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