Plant, Property, and Equipment (Schedule Of Depreciation And Amortization Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation expense - plant, property, and equipment	$ 739	$ 687	$ 591
Total depreciation and amortization expense	881	811	750
Securitized Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	25	25	83
Other Regulatory Asset (Liability) [Member]
Property, Plant and Equipment [Line Items]
Amortization expense			2
Software [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	114	96	70
Other Intangible Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	3	3	4
Consumers Energy Company [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense - plant, property, and equipment	732	680	586
Total depreciation and amortization expense	872	803	744
Consumers Energy Company [Member] | Securitized Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	25	25	83
Consumers Energy Company [Member] | Other Regulatory Asset (Liability) [Member]
Property, Plant and Equipment [Line Items]
Amortization expense			2
Consumers Energy Company [Member] | Software [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	112	95	69
Consumers Energy Company [Member] | Other Intangible Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	$ 3	$ 3	$ 4