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Regulatory Matters (Schedule of GCR Reconciliation Filing Pending with the MPSC) (Details) (USD $) In Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | --- | ---
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | Mar. 31, 2011 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member] | Mar. 31, 2010 Gas Cost Recover (GCR) [Member] Consumers Energy Company [Member] | Sep. 30, 2011 Consumers Energy Company [Member] | Sep. 30, 2010 Consumers Energy Company [Member] | Sep. 30, 2011 Consumers Energy Company [Member] | Sep. 30, 2010 Consumers Energy Company [Member]
Date Of Filing |  |  |  |  | June 2011 | June 2010 |  |  |  |
Net Over/(Under) Recovery, Including Interest, Requested by Consumers |  |  |  |  | $ 6 | $ 1 |  |  |  |
Cost of gas sold | $ 107 | $ 104 | $ 1,095 | $ 1,060 | $ 1,200 | $ 1,300 | $ 88 | $ 92 | $ 1,038 | $ 1,001

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- Definition Net over-/(under-) recovery of expense, including interest, requested by Consumers. + Details
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- Definition Cost of natural gas purchased and associated transportation and storage costs during the period. + Details
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