Leases (Schedule of Lease Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 6	$ 6
Finance lease costs
Amortization of right-of-use assets	9	12
Interest on lease liabilities	15	14
Variable lease costs	107	93
Short-term lease costs	14	23
Total lease costs	151	148
Consumers Energy Company
Lessee, Lease, Description [Line Items]
Operating lease costs	5	6
Finance lease costs
Amortization of right-of-use assets	8	12
Interest on lease liabilities	13	14
Variable lease costs	107	93
Short-term lease costs	14	22
Total lease costs	$ 147	$ 147