Leases (Schedule of Lessee Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Cash paid for amounts included in the measurement of lease liabilities
Cash used in operating activities for operating leases	$ 6	$ 6
Cash used in operating activities for finance leases	15	15
Cash used in financing activities for finance leases	6	8
Lease liabilities arising from obtaining right-of-use assets
Operating leases	3	1
Finance leases	55	0
Consumers Energy Company
Cash paid for amounts included in the measurement of lease liabilities
Cash used in operating activities for operating leases	5	6
Cash used in operating activities for finance leases	13	13
Cash used in financing activities for finance leases	5	8
Lease liabilities arising from obtaining right-of-use assets
Operating leases	1	1
Finance leases	$ 34	$ 0