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Contingencies And Commitments (Contingencies And Commitments) (Details) (USD $) In Millions, unless otherwise specified |  |  |  |  | 9 Months Ended |  |  | 9 Months Ended |  | 1 Months Ended | 9 Months Ended |
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Sep. 30, 2014 | Dec. 31, 2013 | Sep. 30, 2014 Consumers Energy Company [Member] | Dec. 31, 2013 Consumers Energy Company [Member] | Sep. 30, 2014 Bay Harbor [Member] | Oct. 31, 2010 Bay Harbor [Member] | Sep. 30, 2014 CERCLA Liability [Member] Consumers Energy Company [Member] | Sep. 30, 2014 Manufactured Gas Plant [Member] Consumers Energy Company [Member] item | Sep. 30, 2014 Electric Utility [Member] NREPA [Member] Consumers Energy Company [Member] | Sep. 30, 2014 Electric Utility [Member] EPA NOV [Member] Consumers Energy Company [Member] | Sep. 30, 2014 Electric Utility [Member] EPA NOV [Member] Consumers Energy Company [Member] item | Sep. 30, 2014 Gas Utility [Member] NREPA [Member] Consumers Energy Company [Member]
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Environmental remediation permit renewal term |  |  |  |  | 5 years |  |  |  |  |  |  |
Demand for payment by USEPA |  |  |  |  |  | $ 7 |  |  |  |  |  |
Increase in liability due to change in estimates |  |  |  |  | 15 |  |  |  |  |  |  |
Cumulative environmental charge |  |  |  |  | 245 |  |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  |  |  | 63 |  | 3 | 117 | 4 |  |  | 1
Discounted projected costs rate |  |  |  |  | 4.34% |  |  | 2.57% |  |  |  |
Remaining undiscounted obligation amount |  |  |  |  | 82 |  |  | 132 |  |  |  |
Foreign government tax claim on sale | 142 |  |  |  |  |  |  |  |  |  |  |
Remediation and other response activity costs, minimum |  |  |  |  |  |  | 3 |  | 4 |  |  |
Remediation and other response activity costs. maximum |  |  |  |  |  |  | 9 |  | 6 |  |  | 3
Number of boilers alleged to exceed emission limits |  |  |  |  |  |  |  |  |  |  | 14 |
Alleged number of facilities in violation |  |  |  |  |  |  |  |  |  |  | 3 |
Number of projects affected by alleged violations |  |  |  |  |  |  |  |  |  |  | 10 |
Environmental mitigation projects, required investment |  |  |  |  |  |  |  |  |  | 7.7 |  |
Litigation settlement, gross |  |  |  |  |  |  |  |  |  | 2.75 |  |
Number of former MGPs |  |  |  |  |  |  |  | 23 |  |  |  |
Regulatory assets | $ 1,447 | $ 1,530 | $ 1,447 | $ 1,530 |  |  |  | $ 147 |  |  |  |
Authorized recovery, collection period |  |  |  |  |  |  |  | 10 years |  |  |  |
Accrual for environmental loss contingencies, inflation rate |  |  |  |  | 1.00% |  |  | 2.50% |  |  |  |

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