Plant, Property, and Equipment (Schedule of Finite-Lived Intangible Assets by Major Class Table) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	$ 1,134	$ 1,114
Accumulated Amortization	667	615
Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	1,104	1,100
Accumulated Amortization	658	607
Plant additions	2,000	2,000
Plant retirements	220	380
Software development
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	883	882
Accumulated Amortization	577	529
Software development | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	856	869
Accumulated Amortization	568	521
Leasehold improvements
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	10	9
Accumulated Amortization	7	7
Leasehold improvements | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	10	9
Accumulated Amortization	7	7
Intangible Plant | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Plant additions	69	67
Plant retirements	65	193
Rights of way
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	197	180
Accumulated Amortization	57	55
Rights of way | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	197	180
Accumulated Amortization	57	55
Franchises and consents
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	16	16
Accumulated Amortization	10	9
Franchises and consents | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	16	16
Accumulated Amortization	10	9
Other intangible assets
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	28	27
Accumulated Amortization	16	15
Other intangible assets | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	25	26
Accumulated Amortization	$ 16	$ 15
Minimum | Software development
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	1 year
Minimum | Software development | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	3 years
Minimum | Rights of way
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	50 years
Minimum | Rights of way | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	50 years
Minimum | Franchises and consents
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	5 years
Minimum | Franchises and consents | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	5 years
Maximum | Software development
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	15 years
Maximum | Software development | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	15 years
Maximum | Rights of way
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	85 years
Maximum | Rights of way | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	85 years
Maximum | Franchises and consents
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	50 years
Maximum | Franchises and consents | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	50 years