Document & Entity Information	9 Months Ended
	Sep. 30, 2011	Oct. 14, 2011
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2011
Trading Symbol	cms
Entity Registrant Name	CMS Energy Corporation
Entity Central Index Key	0000811156
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
CMS Energy Corporation [Member]
Entity Common Stock, Shares Outstanding		253,560,753
Consumers Energy Company [Member]
Entity Registrant Name	Consumers Energy Company
Entity Central Index Key	0000201533
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		84,108,789