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Regulatory Matters (Narrative) (Details) (USD $) |  |  | 6 Months Ended |  |  | 12 Months Ended |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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Jun. 30, 2011 | Dec. 31, 2010 | Jun. 30, 2011 Power Supply Cost Recover (PSCR) [Member] Consumers Energy Company [Member] Authorized by MPSC [Member] | Jun. 30, 2011 Electric Rate Case [Member] Consumers Energy Company [Member] | Dec. 31, 2010 Electric Rate Case [Member] Consumers Energy Company [Member] | Dec. 31, 2010 Power Supply Cost Recover (PSCR) [Member] Consumers Energy Company [Member] | Mar. 31, 2011 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member] | Mar. 31, 2010 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member] | Jun. 30, 2011 Consumers Energy Company [Member] Electric Decoupling [Member] | Mar. 31, 2011 Consumers Energy Company [Member] Electric Decoupling [Member] | Mar. 31, 2011 Consumers Energy Company [Member] Uncollectible Expense Tracking Mechanism [Member] | Jun. 30, 2011 Consumers Energy Company [Member] Electric Operation and Maintenance Show-Cause Order [Member] | Dec. 31, 2009 Consumers Energy Company [Member] Electric Operation and Maintenance Show-Cause Order [Member] | May 31, 2011 Gas Rate Case [Member] Consumers Energy Company [Member] | Feb. 28, 2011 Gas Rate Case [Member] Consumers Energy Company [Member] | Jan. 31, 2011 Gas Rate Case [Member] Consumers Energy Company [Member] | Aug. 31, 2010 Gas Rate Case [Member] Consumers Energy Company [Member] | Jun. 30, 2011 Consumers Energy Company [Member] Big Rock [Member] | Apr. 30, 2010 Consumers Energy Company [Member] Big Rock [Member] | Feb. 28, 2010 Consumers Energy Company [Member] Big Rock [Member] | Jun. 30, 2011 Consumers Energy Company [Member] Electric Plant [Member] | Feb. 28, 2010 Consumers Energy Company [Member] Electric Plant [Member] | Feb. 28, 2010 Consumers Energy Company [Member] Consumers Share of Ludington [Member] | Jun. 30, 2011 Consumers Energy Company [Member] | May 31, 2011 Consumers Energy Company [Member] | Apr. 30, 2011 Consumers Energy Company [Member] | Dec. 31, 2010 Consumers Energy Company [Member]
Annual Rate Increase Authorized by MPSC |  |  |  |  | $ 146,000,000 |  |  |  |  |  |  |  |  | $ 31,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Annual Rate Increase Requested by Consumers |  |  |  | 195,000,000 |  |  |  |  |  |  |  |  |  |  |  |  | 55,000,000 |  |  |  |  |  |  |  |  |  |
Difference Between the Annual Rate Increase Authorized by MPSC and the Annual Rate Increase Self-implemented by Consumers |  |  |  |  | 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of rates to be refunded to customers |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested Recovery |  |  |  |  |  |  |  |  |  | 27,000,000 | 3,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets | 2,050,000,000 | 2,093,000,000 |  |  |  |  |  |  | 58,000,000 |  |  |  |  |  |  |  |  | 85,000,000 |  |  |  |  |  | 2,050,000,000 |  |  | 2,093,000,000
Percentage of Difference Between Rate Base Expense and Actual Expense To Collect/Refund |  |  |  |  |  |  |  |  |  |  | 80.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Difference Between the Operation and Maintenance Expenditures Ordered by MPSC and the Operation and Maintenance Expenditures Incurred by Consumers During 2007 |  |  |  |  |  |  |  |  |  |  |  |  | 14,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Imposed fine by MPSC |  |  |  |  |  |  |  |  |  |  |  | 65,200 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contribution To Fund Decommissioning Costs Previously Collected |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 44,000,000 |  |  |  |  |  |  |
Revenue Collected in Excess of Costs to Decommission Big Rock, Plus Interest, and Ordered for Refund |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 85,000,000 |  |  |  |  |  |  |  |
Amount Paid to Transfer Ownership and Responsibility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30,000,000 |  |  |  |  |  |  |  |  |
Nuclear Fuel Storage Costs Incurred as a Result of the DOE's Failure to Accept Spent Nuclear Fuel |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 55,000,000 |  |  |  |  |  |  |  |  |
Recommended Renewable Recovery Disallowance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,000,000 |  |  |
Annual Amount Of Reduction Of Renewable Energy Plan Surcharge Billed To Customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 54,000,000 |  |
Authorized Energy Optimization Incentive for Exceeding 2009 Savings Targets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,000,000 |  |
Requested Energy Optimization Incentive for Exceeding 2010 Savings Targets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,000,000 |
Requested Increase In Annual Depreciation Expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 46,000,000 | 9,000,000 |  |  |  |
Authorized increase in depreciation expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,000,000 |  |  |  |  |  |
Rate of Return on Equity Requested |  |  |  | 10.70% |  |  |  |  |  |  |  |  |  |  |  |  | 11.00% |  |  |  |  |  |  |  |  |  |
Rate of Return On Equity Authorized by Public Service Commission |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.50% |  |  |  |  |  |  |  |  |  |  |  |  |
Net Over/(Under) Recovery, Including Interest |  |  | (31,000,000) |  |  | (15,000,000) | 6,000,000 | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount Of Proposed Self-implemented Rate Increase |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 48,000,000 |  |  |  |  |  |  |  |  |  |  |
Revised Amount Of Proposed Self-implemented Rate Increase |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 29,000,000 |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The amount that Consumers paid to transfer ownership and responsibility for the Big Rock ISFSI + Details
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- Definition The annual amount by which the renewable energy plan surcharge billed to customers will be reduced + Details
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- Definition The annual rate increase authorized by the Public Service Commission. + Details
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- Definition The annual rate increase requested by Consumers. + Details
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- Definition Energy optimization incentive that the MPSC authorized Consumers to collect for achieving electric and gas savings targets. + Details
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- Definition Authorized increase in depreciation expense. + Details
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- Definition Contribution To Fund Decommissioning Costs Previously Collected + Details
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- Definition Difference Between Annual Rate Increase Authorized And Self Implemented Annual Rate Increase + Details
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- Definition The difference between the operation and maintenance expenditures authorized by the MPSC and the operation and maintenance expenditures incurred by Consumers. + Details
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- Definition Net over-/(under-) recovery of expense, including interest. + Details
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- Definition Nuclear fuel storage costs incurred by Consumers as a result of the DOE's failure to accept spent nuclear fuel. + Details
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- Definition The percentage of the difference between the level of expense included in rates and actual expense that will be collected or refunded. + Details
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- Definition The rate of return on equity authorized by the Public Service Commission. + Details
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- Definition The rate of return on equity requested by Consumers. + Details
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- Definition Amount of exclusion from recovery through the renewable surcharge recommended by the Administrative Law Judge. + Details
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- Definition Energy optimization incentive requested for achieving electric and gas savings targets. + Details
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- Definition Requested increase in annual depreciation expense. + Details
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- Definition The amount for which Consumers requested recovery. + Details
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- Definition Revenue collected in excess of the costs incurred to decommission, plus interest, and for which the MPSC ordered a refund. + Details
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- Definition The revised annual rate increase proposed to self-implement. + Details
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- Definition Current regulatory liabilities generally represent obligations to make refunds to customers for various reasons including overpayment. + Details
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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 71 -Paragraph 9, 10 -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 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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