Plant, Property, and Equipment (Schedule of Finite-Lived Intangible Assets by Major Class Table) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	$ 1,242,000,000	$ 1,158,000,000
Accumulated Amortization	686,000,000	561,000,000
Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	1,226,000,000	1,143,000,000
Accumulated Amortization	678,000,000	555,000,000
Plant additions	1,800,000,000	1,700,000,000
Plant retirements	190,000,000	214,000,000
Software development
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	1,024,000,000	950,000,000
Accumulated Amortization	603,000,000	481,000,000
Software development | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	1,009,000,000	937,000,000
Accumulated Amortization	595,000,000	475,000,000
Leasehold improvements
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	9,000,000	9,000,000
Accumulated Amortization	7,000,000	7,000,000
Leasehold improvements | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	9,000,000	9,000,000
Accumulated Amortization	7,000,000	7,000,000
Intangible Plant | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Plant additions	90,000,000	100,000,000
Plant retirements	7,000,000	0
Rights of way
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	167,000,000	162,000,000
Accumulated Amortization	52,000,000	50,000,000
Rights of way | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	167,000,000	162,000,000
Accumulated Amortization	52,000,000	50,000,000
Franchises and consents
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	15,000,000	14,000,000
Accumulated Amortization	9,000,000	8,000,000
Franchises and consents | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	15,000,000	14,000,000
Accumulated Amortization	9,000,000	8,000,000
Other intangible assets
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	27,000,000	23,000,000
Accumulated Amortization	15,000,000	15,000,000
Other intangible assets | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Gross cost	26,000,000	21,000,000
Accumulated Amortization	$ 15,000,000	$ 15,000,000
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	30 years
Maximum | Franchises and consents | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Amortization Life in Years	30 years