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Contingencies and Commitments (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended |  |  |  |  |  |  | 1 Months Ended |  |  | 3 Months Ended
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Mar. 31, 2012 | Mar. 31, 2011 | Dec. 31, 2011 | Oct. 31, 2010 | Dec. 31, 2004 | Mar. 31, 2012 Consumers Energy Company [Member] | Dec. 31, 2011 Consumers Energy Company [Member] | Mar. 31, 2012 NREPA [Member] Consumers Energy Company [Member] | Mar. 31, 2012 Superfund Liability [Member] Consumers Energy Company [Member] | Jul. 31, 2011 Nuclear Fuel Disposal Cost [Member] Consumers Energy Company [Member] | Jun. 30, 2011 Nuclear Fuel Disposal Cost [Member] Consumers Energy Company [Member] | Jun. 30, 2011 Spent Nuclear Fuel Principal [Member] Consumers Energy Company [Member] | Jun. 30, 2011 Spent Nuclear Fuel Interest [Member] Consumers Energy Company [Member] | Mar. 31, 2012 Manufactured Gas Plant [Member] Consumers Energy Company [Member] | Mar. 31, 2012 Indemnification Expiration [Member]
Demand For Payment By USEPA |  |  |  | $ 7 |  |  |  |  |  |  |  |  |  |  |
Cumulative Environmental Charge | 225 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Recorded liability | 71 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accrual for Environmental Loss Contingencies |  |  |  |  |  |  |  | 1 | 2 |  |  |  |  | 128 |
Spent Nuclear Fuel Obligation, Noncurrent |  |  |  |  |  |  |  |  |  |  | 163 | 44 | 119 |  |
Discounted projected costs rate | 4.34% |  |  |  |  |  |  |  |  |  |  |  |  | 2.57% |
Site Contingency Accrual Inflation Rate | 1.00% |  |  |  |  |  |  |  |  |  |  |  |  | 2.50% |
Remaining undiscounted obligation amount | 95 |  |  |  |  |  |  |  |  |  |  |  |  | 141 |
Undiscounted amount due within one year | 16 |  |  |  |  |  |  |  |  |  |  |  |  | 11 |
Undiscounted amount due within two year | 8 |  |  |  |  |  |  |  |  |  |  |  |  | 11 |
Undiscounted amount due within third year | 4 |  |  |  |  |  |  |  |  |  |  |  |  | 11 |
Undiscounted amount due within fourth year | 4 |  |  |  |  |  |  |  |  |  |  |  |  | 20 |
Undiscounted amount due within five year | 5 |  |  |  |  |  |  |  |  |  |  |  |  | 11 |
Foreign Government Tax Claim On Sale |  |  |  |  | 142 |  |  |  |  |  |  |  |  |  |
After Tax Income in Discontinued Operations Recognized After Expiration of Tax Indemnification | 7 | 2 |  |  |  |  |  |  |  |  |  |  |  |  | 7
Remediation and other response activity costs, minimum |  |  |  |  |  |  |  | 1 | 2 |  |  |  |  |  |
Remediation and other response activity costs. maximum |  |  |  |  |  |  |  | 4 | 8 |  |  |  |  |  |
Litigation Settlement, Gross |  |  |  |  |  |  |  |  |  | 120 |  |  |  |  |
Regulatory assets, noncurrent | 2,362 |  | 2,466 |  |  | 2,362 | 2,466 |  |  |  |  |  |  | 155 |
Regulatory Liability, Noncurrent | 1,919 |  | 1,875 |  |  | 1,919 | 1,875 |  |  |  |  |  |  |  |
Number of former MGPs |  |  |  |  |  | 23 |  |  |  |  |  |  |  |  |
Carrying Amounts |  |  |  |  |  | 1 |  |  |  |  |  |  |  |  |
Maximum Obligation |  |  |  |  |  | $ 30 |  |  |  |  |  |  |  |  |

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- Definition Estimated undiscounted amount of the accrual for the environmental loss contingencies at an individual site as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 96-1 -Paragraph 132, 161, 163 -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 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 + Details
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