Income Taxes (Loss and Credit Carryforwards) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Total tax attributes	$ 806
Consumers Energy Company [Member]
Total tax attributes	67
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards	1,403
Net operating loss carryforward	491
Internal Revenue Service (IRS) [Member] \| Consumers Energy Company [Member]
Operating Loss Carryforwards	134
Net operating loss carryforward	47
Local Jurisdiction [Member]
Operating Loss Carryforwards	439
State and local net operating loss carryforwards	4
Valuation Allowance - Loss carryforward	2
State Jurisdiction [Member]
Operating Loss Carryforwards	26
State and local net operating loss carryforwards	2
Valuation Allowance - Loss carryforward	2
State Jurisdiction [Member] \| Consumers Energy Company [Member]
Operating Loss Carryforwards	10
Net operating loss carryforward	1
Valuation Allowance - Loss carryforward	1
Alternative Minimum Tax [Member]
Tax Credit Carryforward, Amount	269
AMT credits	269
Alternative Minimum Tax [Member] \| Consumers Energy Company [Member]
Tax Credit Carryforward, Amount	5
AMT credits	5
General Business [Member]
Tax Credit Carryforward, Amount	40
General business credits	40
Valuation Allowance - General business credits	2
General Business [Member] \| Consumers Energy Company [Member]
Tax Credit Carryforward, Amount	14
General business credits	$ 14

The sum of the tax effects as of the balance sheet date of the amount of excesses of tax deductions over gross income in a year which cannot be used on the tax returns in the current year but can be carried forward to reduce taxable income or income taxes payable in a future year, for which there must be sufficient tax-basis income to utilize a portion or all of the carryforward amount to realize the deferred tax asset.

+ References+ Details

The tax effect as of the balance sheet date of the amount of excess of tax deductions over gross income in a year which cannot be used on the tax return of a state or local jurisdiction in the current year but can be carried forward to reduce taxable income or income taxes payable in a future year, for which there must be sufficient tax-basis income to utilize a portion or all of the carryforward amount to realize the deferred tax asset.

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- Definition

The tax effect as of the balance sheet date of the amount of future tax deductions arising from unused alternative minimum tax credit carryforwards; a tax credit carryforward is the amount by which tax credits available for utilization exceeded statutory limits on inclusion in historical filings, and which can only be utilized if sufficient tax-basis income is generated in future periods and providing tax laws continue to allow such utilization.

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- Definition

The tax effect as of the balance sheet date of the amount of future tax deductions arising from unused general business tax credit carryforwards. The general business tax credits are the sum of numerous tax credits which include, but are not limited to, investment tax , alcohol fuels, low income housing, alternative fuels, alternative motor vehicles, hurricane relief, disabled access, renewable resources electricity production, employer social security, orphan drug, new markets, employer provided child care facilities and services, biodiesel fuels, low sulfur diesel fuel production, distilled spirits, and the advanced nuclear power facilities credit. A tax credit carryforward is the amount by which tax credits available for utilization exceeded statutory limits on inclusion in historical filings. They can only be utilized if sufficient tax-basis income is generated in future periods and providing tax laws continue to allow such utilization.

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- Definition

The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 43

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 30

-Paragraph 5

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6907311&loc=d3e30536-109315

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 17

-Subparagraph e

-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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 48

-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.

+ Details

- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References+ Details

- Definition

The portion of the deferred tax asset arising from a tax credit carryforward for which it is more likely than not that a tax benefit will not be realized.

+ References+ Details