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Plant, Property, and Equipment (Schedule of Finite Lived Intangible Assets Amortization Expense) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Amortization of Intangible Assets | $ 48 | $ 39 | $ 32
Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Amortization of Intangible Assets | 47 | 38 | 32
Software and Software Development Costs [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Amortization of Intangible Assets | 39 | 31 | 24
Software and Software Development Costs [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Amortization of Intangible Assets | 39 | 30 | 24
Minimum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Expected future amortization expense of intangible assets, per year | 54 |  |
Minimum [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Expected future amortization expense of intangible assets, per year | 54 |  |
Maximum [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Expected future amortization expense of intangible assets, per year | 73 |  |
Maximum [Member] | Consumers Energy Company [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Expected future amortization expense of intangible assets, per year | $ 73 |  |

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275 + Details
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