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Plant, Property, and Equipment (Plant, Property, and Equipment Table) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Construction work in progress |  | $ 1,509 | $ 1,106
Less accumulated depreciation and amortization |  | (5,747) | (5,415)
Total plant, property, and equipment | [1] | 14,705 | 13,412
Public Utilities, Property Plant and Equipment Additions |  | 1,400 | 1,600
Public Utilities, Property Plant and Equipment Disposals |  | 187 | 126
Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Construction work in progress |  | 1,467 | 1,103
Less accumulated depreciation and amortization |  | (5,676) | (5,346)
Total plant, property, and equipment | [1] | 14,588 | 13,337
Public Utilities, Property Plant and Equipment Additions |  | 1,400 | 1,600
Public Utilities, Property Plant and Equipment Disposals |  | 187 | 126
Electricity Generation Plant, Non-Nuclear [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Generation or Processing |  | $ 4,925 | 4,544
Electricity Generation Plant, Non-Nuclear [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Generation |  | 22 years |
Electricity Generation Plant, Non-Nuclear [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Generation |  | 125 years |
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Generation or Processing |  | $ 4,925 | 4,544
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Generation |  | 22 years |
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Generation |  | 125 years |
Electric Distribution [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Distribution |  | $ 6,809 | 6,487
Electric Distribution [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 20 years |
Electric Distribution [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 75 years |
Electric Distribution [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Distribution |  | $ 6,809 | 6,487
Electric Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 20 years |
Electric Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 75 years |
Electric Other [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment |  | $ 1,039 | 910
Electric Other [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 5 years |
Electric Other [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 50 years |
Electric Other [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment |  | $ 1,039 | 910
Electric Other [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 5 years |
Electric Other [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 50 years |
Electric Capital Leases [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Capital leases and financing obligation |  | $ 286 | 289
Electric Capital Leases [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Capital leases and financing obligation |  | 286 | 289
Gas Distribution [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Distribution |  | $ 3,497 | 3,239
Gas Distribution [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 28 years |
Gas Distribution [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 80 years |
Gas Distribution [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Distribution |  | $ 3,497 | 3,239
Gas Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 28 years |
Gas Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Distribution |  | 80 years |
Gas Transmission [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Transmission |  | $ 981 | 974
Gas Transmission [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Transmission |  | 17 years |
Gas Transmission [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Transmission |  | 75 years |
Gas Transmission [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Transmission |  | $ 981 | 974
Gas Transmission [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Transmission |  | 17 years |
Gas Transmission [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Transmission |  | 75 years |
Gas Underground Storage Facilities [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment | [2] | $ 601 | 578
Gas Underground Storage Facilities [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other | [2] | 29 years |
Gas Underground Storage Facilities [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other | [2] | 65 years |
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment | [2] | $ 601 | 578
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other | [2] | 29 years |
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other | [2] | 65 years |
Gas Other [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment |  | $ 630 | 538
Gas Other [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 5 years |
Gas Other [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 50 years |
Gas Other [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment |  | $ 630 | 538
Gas Other [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 5 years |
Gas Other [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 50 years |
Gas Capital Leases [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Capital leases and financing obligation |  | $ 14 | 6
Gas Capital Leases [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Capital leases and financing obligation |  | 14 | 6
Natural Gas [Member] | Gas Underground Storage Facilities [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment |  | 26 | 26
Natural Gas [Member] | Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment |  | 26 | 26
Enterprises IPP [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Plant, property, and equipment, gross |  | $ 95 | 90
Enterprises IPP [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 3 years |
Enterprises IPP [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 30 years |
Enterprises Other [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Plant, property, and equipment, gross |  | $ 25 | 25
Enterprises Other [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 3 years |
Enterprises Other [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 40 years |
Other [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Other non-utility property |  | $ 41 | 41
Other [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 2 years |
Other [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 51 years |
Other [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Other non-utility property |  | $ 15 | $ 15
Other [Member] | Consumers Energy Company [Member] | Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 8 years |
Other [Member] | Consumers Energy Company [Member] | Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Estimated Depreciable Life in Years, Other |  | 51 years |
[1] | For the year ended December 31, 2015, utility plant additions were $1.4 billion and utility plant retirements were $187 million. For the year ended December 31, 2014, utility plant additions were $1.6 billion and utility plant retirements were $126 million.
[2] | Underground storage includes base natural gas of $26 million at December 31, 2015 and 2014. Base natural gas is not subject to depreciation.

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