Plant, Property, and Equipment (Public Utilities Property Plant and Equipment Schedule of Accumulated Depreciation and Amortization) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization	$ 6,056	$ 5,747
Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	5,994	5,676
Utility Plant Assets [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization	5,993	5,674
Utility Plant Assets [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	5,993	5,674
Non-Utility Plant Assets [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization	63	73
Non-Utility Plant Assets [Member] | Consumers Energy Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ 1	$ 2