Document & Entity Information
9 Months Ended
Sep. 30, 2011
Oct. 14, 2011
Document Type10-Q 
Amendment Flagfalse 
Document Period End DateSep. 30, 2011 
Document Fiscal Period FocusQ3 
Document Fiscal Year Focus2011 
Trading Symbolcms 
Entity Registrant NameCMS Energy Corporation 
Entity Central Index Key0000811156 
Current Fiscal Year End Date--12-31 
Entity Filer CategoryLarge Accelerated Filer 
CMS Energy Corporation [Member]
  
Entity Common Stock, Shares Outstanding 253,560,753
Consumers Energy Company [Member]
  
Entity Registrant NameConsumers Energy Company 
Entity Central Index Key0000201533 
Entity Filer CategoryNon-accelerated Filer 
Entity Common Stock, Shares Outstanding 84,108,789