Financings and Capitalization (Issuance of Convertible Senior Notes) (Details) $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2023 USD ($) d	Jan. 31, 2024 USD ($)	Dec. 31, 2023 USD ($) $ / shares
Debt Instrument [Line Items]
Principal (In Millions)			$ 3,556
Consumers Energy Company
Debt Instrument [Line Items]
Principal (In Millions)			2,671
CMS Energy
Debt Instrument [Line Items]
Principal (In Millions)			800
3.375% Convertible Senior Notes Due 2028 | Convertible debt | CMS Energy
Debt Instrument [Line Items]
Principal (In Millions)	$ 800		$ 800
Interest rate	3.375%		3.375%
Unamortized issuance costs	$ 12
Conversion price (in dollars per share) | $ / shares			$ 73.97
Threshold percentage of stock price trigger	130.00%
Threshold trading days | d	20
Threshold consecutive trading days | d	30
Redemption price percentage	100.00%
4.600% First Mortgage Bonds Due May 2029 | First mortgage bonds | Consumers Energy Company | Subsequent Event
Debt Instrument [Line Items]
Principal (In Millions)		$ 600
Interest rate		4.60%