XML 53 R35.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Regulatory Matters (Narrative) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Jul. 26, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Feb. 28, 2018 | Oct. 31, 2017 | Sep. 30, 2017 | Mar. 31, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017 | May 31, 2018
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory liabilities |  | $ 159 |  |  |  |  |  | $ 159 |  | $ 159 |  | $ 80 |
Revenue |  |  |  |  |  |  |  | 1,492 | $ 1,449 | 3,445 | $ 3,278 |  |
Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory liabilities |  | 159 |  |  |  |  |  | 159 |  | 159 |  | 80 |
Revenue |  |  |  |  |  |  |  | 1,395 | $ 1,362 | 3,250 | $ 3,099 |  |
Revenue Subject to Refund - Tax Reform Rate Change | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory liabilities |  | 88 |  |  |  |  |  | 88 |  | 88 |  |  |
Electric Rate Case | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Annual rate increase requested |  |  |  |  |  |  | $ 173 |  |  |  |  |  |
Rate of return on equity requested |  |  |  |  |  |  | 10.50% |  |  |  |  |  |
Annual rate increase requested, amended |  |  |  |  |  | $ 148 |  |  |  |  |  |  |
Annual rate increase self-implemented |  |  |  |  | $ 130 |  |  |  |  |  |  |  |
Annual rate increase authorized |  | 72 | $ 66 |  |  |  |  |  |  |  |  |  |
Rate of return on equity authorized |  |  | 10.00% |  |  |  |  |  |  |  |  |  |
Electric Rate Case | Revenue Subject to Refund - Other | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory liabilities |  | 35 |  |  |  |  |  | $ 35 |  | $ 35 |  |  |
Gas Rate Case | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Recommended disallowance of cost recovery |  |  |  | $ 115 |  |  |  |  |  |  |  |  |
Gas Rate Case Tax Reform Rate Change | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Annual rate increase authorized |  | $ (49) |  |  |  |  |  |  |  |  |  |  |
Energy Waste Reduction Plan | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Requested recovery/collection |  |  |  |  |  |  |  |  |  |  |  |  | $ 31
Revenue |  |  |  |  |  |  |  |  |  |  |  | $ 31 |
Subsequent Event | Gas Rate Case | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Recommended disallowance of cost recovery | $ 100 |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event | Electric Rate Case Tax Reform Rate Change | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Annual rate increase authorized | (113) |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Subsequent Event | Gas Rate Case | Consumers Energy Company |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Disallowed costs for recently completed plant | $ 145 |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition The public utility's regulatory agency recommended amount of disallowed costs for rate making purposes for recently completed plants in regulated industries. + References No definition available. + Details
Name: | cms_PublicUtilitiesPropertyPlantAndEquipmentAmountOfRecommendedDisallowedCostsForRecentlyCompletedPlant
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Potential amount of disallowed costs for rate making purposes for recently completed plants in regulated industries + References No definition available. + Details
Name: | cms_PublicUtilitiesPropertyPlantAndEquipmentPotentialAmountOfDisallowedCostsForRecentlyCompletedPlant
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount requested from regulatory entity for the recovery/collection from customers. + References No definition available. + Details
Name: | cms_RequestedRecoveryCollection
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's approved return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesInterimRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of public utility's amended requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmendedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
Name: | us-gaap_RegulatoryLiabilityCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_Revenues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=cms_ConsumersEnergyCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=cms_RevenueSubjectToRefundTaxReformRateChangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cms_ElectricRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=cms_RevenueSubjectToRefundOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cms_GasRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cms_GasRateCaseTaxReformRateChangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cms_EnergyWasteReductionPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cms_ElectricRateCaseTaxReformRateChangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |