Plant, Property, and Equipment (Schedule Of Depreciation And Amortization Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Depreciation expense - plant, property, and equipment	$ 591	$ 551	$ 516
Total depreciation and amortization expense	750	685	628
Securitized Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	83	75	63
Other Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	2	5	6
Software [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	70	50	40
Other Intangible Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	4	4	3
Consumers Energy Company [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense - plant, property, and equipment	586	546	511
Total depreciation and amortization expense	744	678	622
Consumers Energy Company [Member] | Securitized Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	83	75	63
Consumers Energy Company [Member] | Other Regulatory Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	2	5	6
Consumers Energy Company [Member] | Software [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	69	49	39
Consumers Energy Company [Member] | Other Intangible Assets [Member]
Property, Plant and Equipment [Line Items]
Amortization expense	$ 4	$ 3	$ 3