Document And Entity Information	3 Months Ended
	Mar. 31, 2013	Apr. 08, 2013
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2013
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2013
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 [Member]
Entity Common Stock, Shares Outstanding		266,826,444
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