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Derivative Instruments (Tables)
3 Months Ended
Mar. 31, 2012
Derivative Instruments [Abstract]  
Gain/(Loss) Recognized in Income for Derivative Instruments
In Millions    

 

 
  Location of Gain (Loss) on Derivatives Recognized in Income    Amount of Gain (Loss) on Derivatives  
Recognized in Income  
 

 

 
  Three Months Ended March 31         2012          2011    

 

 

  CMS ENERGY

          

  Commodity contracts

          

Operating revenue

        $          4           $         1     

Fuel for electric generation

        (2        -     

Purchased and interchange power

        (1        -     

 

 

  Total CMS Energy

        $          1           $         1