Transition Activities - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended	45 Months Ended
	May 31, 2023 USD ($) MW	Jun. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Jun. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Dec. 31, 2022 USD ($)
New Covert Generating Facility | Consumers Energy Company
Restructuring Cost and Reserve [Line Items]
Nameplate capacity (in MW) | MW	1,200
Consideration transferred	$ 810
Net book value of plant	440
Plant acquisition adjustment	370
Increase to property, plant, and equipment	810
New Covert Generating Facility | Seller
Restructuring Cost and Reserve [Line Items]
Original cost of plant	665
Accumulated depreciation	$ 225
D.E. Karn Generating Complex | Consumers Energy Company | Costs of coal-fueled electric generating units to be retired
Restructuring Cost and Reserve [Line Items]
Regulatory assets, number of units | coal_fueled_electric_generating_unit		2		2		2	2
Regulatory asset		$ 670		$ 670		$ 670	$ 670
Retention Benefits
Restructuring Cost and Reserve [Line Items]
Cost deferred		$ 5	$ 2	$ 10	$ 3
Retention Benefits | D.E. Karn Generating Complex and J.H. Campbell Generating Units | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Regulatory asset collection period		3 years		3 years		3 years	3 years
Retention Benefits | D.E. Karn Generating Complex
Restructuring Cost and Reserve [Line Items]
Aggregate cost incurred								$ 32
Retention and severance costs							$ 16
Retention Benefits | D.E. Karn Generating Complex | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Cost deferred							12
Retention Benefits | D.E. Karn Generating Complex | Property, Plant and Equipment
Restructuring Cost and Reserve [Line Items]
Costs incurred and capitalized							4
Retention Benefits | J.H. Campbell Generating Units
Restructuring Cost and Reserve [Line Items]
Expected cost		$ 50		$ 50		$ 50	$ 50
Retention Benefits | J.H. Campbell Generating Units | Retention Incentive Program
Restructuring Cost and Reserve [Line Items]
Cost deferred						$ 28