Leases (Schedule of Lease Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Lessee, Lease, Description [Line Items]
Operating lease costs	$ 4	$ 6
Finance lease costs
Amortization of right-of-use assets	8	6
Interest on lease liabilities	18	16
Variable lease costs	115	107
Short-term lease costs	25	13
Total lease costs	170	148
Consumers Energy Company
Lessee, Lease, Description [Line Items]
Operating lease costs	4	5
Finance lease costs
Amortization of right-of-use assets	6	5
Interest on lease liabilities	14	13
Variable lease costs	115	107
Short-term lease costs	24	12
Total lease costs	$ 163	$ 142