Plant, Property, and Equipment (Schedule Of Depreciation And Amortization) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ 7,037	$ 6,510
Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	6,958	6,441
Utility plant assets
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	6,956	6,439
Utility plant assets | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	6,956	6,439
Non-utility plant assets
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	81	71
Non-utility plant assets | Consumers Energy Company
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ 2	$ 2