Related Party Transactions - Consumers (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) MW	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Consumers Energy Company
Related Party Transaction [Line Items]
Purchased power – related parties	$ 77,000,000	$ 64,000,000	$ 75,000,000
Due to related parties	22,000,000	13,000,000
Accounts receivable related parties	$ 7,000,000	$ 16,000,000
Consumers Energy Company | Enterprise Segment Generating Units
Related Party Transaction [Line Items]
Nameplate capacity (in MW) | MW	1,001
Long-term purchase commitment, amount	$ 515,000,000
Consumers Energy Company | Credit Agreement
Related Party Transaction [Line Items]
Interest rate	0.00%
Maximum borrowing capacity	$ 500,000,000
CMS Energy Note Payable
Related Party Transaction [Line Items]
Interest rate	4.10%
CMS Energy Note Payable | Consumers Energy Company
Related Party Transaction [Line Items]
Interest rate	4.10%