Leases (Summary of Lease Right-of-Use Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Lessor, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other	Other
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other non‑current liabilities	Other non‑current liabilities
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Plant, property, and equipment, net	Plant, property, and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Current portion of long-term debt and finance leases	Current portion of long-term debt and finance leases
Operating leases
Right-of-use assets	$ 26	$ 31
Lease liabilities
Current lease liabilities	4	4
Noncurrent lease liabilities	22	27
Finance leases
Right-of-use assets	71	82
Lease liabilities
Current lease liabilities	5	9
Non-current lease liabilities	$ 62	$ 68
Weighted-average remaining lease term (in years)
Operating leases	19 years	20 years
Finance leases	19 years	18 years
Weighted-average discount rate
Operating leases	5.20%	4.00%
Finance leases	5.30%	5.20%
Finance lease liability	$ 67
Consumers Energy Company
Operating leases
Right-of-use assets	23	$ 27
Lease liabilities
Current lease liabilities	4	4
Noncurrent lease liabilities	19	23
Finance leases
Right-of-use assets	48	58
Lease liabilities
Current lease liabilities	5	9
Non-current lease liabilities	$ 39	$ 45
Weighted-average remaining lease term (in years)
Operating leases	18 years	18 years
Finance leases	11 years	10 years
Weighted-average discount rate
Operating leases	5.30%	3.90%
Finance leases	1.50%	1.60%
Finance lease liability	$ 44
Related Party Lease
Lease liabilities
Current lease liabilities	1	$ 1
Weighted-average discount rate
Finance lease liability	$ 24	$ 24