Contingencies And Commitments (Contingencies And Commitments) (Details) (USD $)
In Millions, unless otherwise specified
 9 Months Ended 1 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2011
Oct. 31, 2010
Sep. 30, 2012
Consumers Energy Company [Member]
Dec. 31, 2011
Consumers Energy Company [Member]
Sep. 30, 2012
NREPA [Member]
Consumers Energy Company [Member]
Sep. 30, 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]
Sep. 30, 2012
Manufactured Gas Plant [Member]
Consumers Energy Company [Member]
item
Demand for payment by USEPA       $ 7                  
Cumulative environmental charge 226                        
Recorded liability 64                       125
Accrual for environmental loss contingencies             4 2          
Discounted projected costs rate 4.34%                       2.57%
Site contingency accrual inflation rate 1.00%                       2.50%
Remaining undiscounted obligation amount 85                       137
Undiscounted amount due within one year 4                       7
Undiscounted amount due within two year 10                       11
Undiscounted amount due within third year 5                       11
Undiscounted amount due within fourth year 4                       20
Undiscounted amount due within five year 4                       11
Foreign government tax claim on sale 142                        
After tax income in discontinued operations recognized after expiration of tax indemnification 7 2                      
Remediation and other response activity costs, minimum             4 2          
Remediation and other response activity costs. maximum             7 8          
Litigation settlement, gross                 120        
Spent nuclear fuel obligation, noncurrent                   163 44 119  
Number of former MGPs                         23
Regulatory assets, noncurrent $ 2,273   $ 2,466   $ 2,273 $ 2,466             $ 153