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Plant, Property, and Equipment (Schedule of Finite-Lived Intangible Assets by Major Class Table) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | $ 1,052 | $ 930
Finite-Lived Intangible Assets, Accumulated Amortization |  | 444 | 368
Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 1,043 | 925
Finite-Lived Intangible Assets, Accumulated Amortization |  | 440 | 365
Public Utilities, Property Plant and Equipment Additions |  | 2,300 | 1,400
Public Utilities, Property Plant and Equipment Disposals |  | 285 | 187
Software Development Costs [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 853 | 734
Finite-Lived Intangible Assets, Accumulated Amortization |  | 367 | 294
Software Development Costs [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 845 | 729
Finite-Lived Intangible Assets, Accumulated Amortization |  | 363 | 291
Leasehold Improvements [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1],[2] | 7 | 7
Finite-Lived Intangible Assets, Accumulated Amortization | [2] | 6 | 5
Leasehold Improvements [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1],[2] | 7 | 7
Finite-Lived Intangible Assets, Accumulated Amortization | [2] | 6 | 5
Intangible Plant [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property Plant and Equipment Additions |  | 141 | 140
Public Utilities, Property Plant and Equipment Disposals |  | 23 |
Rights of Way [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 155 | 153
Finite-Lived Intangible Assets, Accumulated Amortization |  | 48 | 46
Rights of Way [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 155 | 153
Finite-Lived Intangible Assets, Accumulated Amortization |  | 48 | 46
Franchises and Consents [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 15 | 15
Finite-Lived Intangible Assets, Accumulated Amortization |  | 8 | 8
Franchises and Consents [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 15 | 15
Finite-Lived Intangible Assets, Accumulated Amortization |  | 8 | 8
Other Intangible Assets [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 22 | 21
Finite-Lived Intangible Assets, Accumulated Amortization |  | 15 | 15
Other Intangible Assets [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Assets, Gross | [1] | 21 | 21
Finite-Lived Intangible Assets, Accumulated Amortization |  | $ 15 | $ 15
Minimum [Member] | Software Development Costs [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 1 year |
Minimum [Member] | Software Development Costs [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 3 years |
Minimum [Member] | Rights of Way [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 50 years |
Minimum [Member] | Rights of Way [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 50 years |
Minimum [Member] | Franchises and Consents [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 5 years |
Minimum [Member] | Franchises and Consents [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 5 years |
Maximum [Member] | Software Development Costs [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 15 years |
Maximum [Member] | Software Development Costs [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 15 years |
Maximum [Member] | Rights of Way [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 75 years |
Maximum [Member] | Rights of Way [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 75 years |
Maximum [Member] | Franchises and Consents [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 30 years |
Maximum [Member] | Franchises and Consents [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 30 years |
[1] | For the year ended December 31, 2016, Consumers' intangible asset additions were $141 million and intangible asset retirements were $23 million. For the year ended December 31, 2015, Consumers' intangible asset additions were $140 million and there were no retirements.
[2] | Leasehold improvements are amortized over the life of the lease, which may change whenever the lease is renewed or extended.

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- Definition Current year acquisitions of long-lived assets used in the normal conduct of business and not intended for resale. Examples include land, buildings, machinery and equipment, certain intangible assets, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software. + References No definition available. + Details
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