Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Jan. 14, 2019	Jun. 30, 2018
Document Information [Line Items]
Entity Registrant Name	CMS Energy Corporation
Trading Symbol	cms
Entity Central Index Key	0000811156
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filer	No
Entity Current Reporting Status	Yes
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Public Float			$ 13,332
Entity Common Stock, Shares Outstanding		283,400,105
Consumers Energy Company
Document Information [Line Items]
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