Financings and Capitalization (Debt Maturities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 635
Long-term Debt, Maturities, Repayments of Principal in Year Two	631
Long-term Debt, Maturities, Repayments of Principal in Year Three	527
Long-term Debt, Maturities, Repayments of Principal in Year Four	725
Long-term Debt, Maturities, Repayments of Principal in Year Five	369
Consumers Energy Company [Member]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	339
Long-term Debt, Maturities, Repayments of Principal in Year Two	416
Long-term Debt, Maturities, Repayments of Principal in Year Three	243
Long-term Debt, Maturities, Repayments of Principal in Year Four	323
Long-term Debt, Maturities, Repayments of Principal in Year Five	$ 350

Amount of long-term debt maturing within the next twelve months following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 10

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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Amount of long-term debt maturing in year five following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates.

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Amount of long-term debt maturing in year four following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates.

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Amount of long-term debt maturing in year three following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed of determinable prices and dates.

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Amount of long-term debt maturing in year two following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates.

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