Transition Activities - Narrative (Details) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended		15 Months Ended	48 Months Ended
	Aug. 31, 2023 USD ($)	May 31, 2023 USD ($) MW	Sep. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Sep. 30, 2023 USD ($) coal_fueled_electric_generating_unit	Dec. 31, 2022 USD ($)
Covert Plant Acquisition
Restructuring Cost and Reserve [Line Items]
Consideration transferred	$ 2	$ 810			$ 812	$ 0
Consumers Energy Company | Covert Plant Acquisition
Restructuring Cost and Reserve [Line Items]
Consideration transferred					$ 812	0
New Covert Generating Facility | Consumers Energy Company
Restructuring Cost and Reserve [Line Items]
Nameplate capacity (in MW) | MW		1,200
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			$ 655		$ 655		$ 655	$ 655
Retention Benefits
Restructuring Cost and Reserve [Line Items]
Cost deferred			$ 4	$ 11	$ 14	$ 14
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							$ 32