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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, 2020 | Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | $ 1,134 | $ 1,114
Accumulated Amortization | 667 | 615
Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 1,104 | 1,100
Accumulated Amortization | 658 | 607
Plant additions | 2,000 | 2,000
Plant retirements | 220 | 380
Software development |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 883 | 882
Accumulated Amortization | 577 | 529
Software development | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 856 | 869
Accumulated Amortization | 568 | 521
Leasehold improvements |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 10 | 9
Accumulated Amortization | 7 | 7
Leasehold improvements | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 10 | 9
Accumulated Amortization | 7 | 7
Intangible Plant | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Plant additions | 69 | 67
Plant retirements | 65 | 193
Rights of way |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 197 | 180
Accumulated Amortization | 57 | 55
Rights of way | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 197 | 180
Accumulated Amortization | 57 | 55
Franchises and consents |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 16 | 16
Accumulated Amortization | 10 | 9
Franchises and consents | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 16 | 16
Accumulated Amortization | 10 | 9
Other intangible assets |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 28 | 27
Accumulated Amortization | 16 | 15
Other intangible assets | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Gross cost | 25 | 26
Accumulated Amortization | $ 16 | $ 15
Minimum | Software development |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 1 year |
Minimum | Software development | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 3 years |
Minimum | Rights of way |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 50 years |
Minimum | Rights of way | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 50 years |
Minimum | Franchises and consents |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 5 years |
Minimum | Franchises and consents | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 5 years |
Maximum | Software development |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 15 years |
Maximum | Software development | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 15 years |
Maximum | Rights of way |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 85 years |
Maximum | Rights of way | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 85 years |
Maximum | Franchises and consents |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 50 years |
Maximum | Franchises and consents | Consumers Energy Company |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |
Amortization Life in Years | 50 years |

X
- 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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