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Regulatory Matters (Narrative) (Details) $ in Millions | 1 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Apr. 30, 2016 USD ($) item | Jan. 31, 2016 USD ($) | Nov. 30, 2015 USD ($) | Jul. 31, 2015 USD ($) | Jun. 30, 2015 USD ($) | Dec. 31, 2014 USD ($) | Jun. 30, 2016 USD ($) | Dec. 31, 2015 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Regulatory liability current |  |  |  |  |  |  | $ 78 | $ 82
Electric Transmission [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Change in net plant, property, and equipment | $ 34 |  |  |  |  |  |  |
Consumers Energy Company [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Regulatory liability current |  |  |  |  |  |  | 78 | 82
Electric Rate Case [Member] | Consumers Energy Company [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Annual rate increase requested |  |  |  |  |  | $ 163 |  |
Rate of return on equity requested |  |  |  |  |  | 10.70% |  |
Annual rate increase self-implemented |  |  |  |  | $ 110 |  |  |
Annual rate increase authorized | $ 126 |  |  |  |  |  |  |
Rate of return on equity authorized |  |  | 10.30% |  |  |  |  |
Temporary rate increase |  |  | $ 165 |  |  |  |  |
Number of units retired | item | 7 |  |  |  |  |  |  |
Electric Rate Case [Member] | Self-Implemented Rate Refunds [Member] | Consumers Energy Company [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Regulatory liability current |  |  |  |  |  |  | 1 |
Gas Rate Case [Member] | Consumers Energy Company [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Annual rate increase requested |  |  |  | $ 85 |  |  |  |
Rate of return on equity requested |  |  |  | 10.70% |  |  |  |
Annual rate increase self-implemented |  | $ 60 |  |  |  |  |  |
Annual rate increase authorized | $ 40 |  |  |  |  |  |  |
Gas Rate Case [Member] | Self-Implemented Rate Refunds [Member] | Consumers Energy Company [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Regulatory liability current |  |  |  |  |  |  | 10 |
Energy Optimization Plan Incentive [Member] | Consumers Energy Company [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Requested recovery/collection |  |  |  |  |  |  |  | $ 18
Current FERC Revenue Requirement [Member] | Electric Transmission [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Revenue requirement |  |  |  |  |  |  | 9 |
METC Proposed FERC Revenue Requirement [Member] | Electric Transmission [Member] |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Revenue requirement |  |  |  |  |  |  | $ 6 |

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