Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,758	$ 1,957
Leasing income	39	48
Financing income	67	54
Total operating revenue	1,864	2,059
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	19	19
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,739	1,938
Financing income	5	5
Total operating revenue	1,744	1,943
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	974	1,112
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	488	525
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	160	187
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	117	114
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,025	1,100
Financing income	3	3
Total operating revenue	1,028	1,103
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	714	838
Financing income	2	2
Total operating revenue	716	840
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	19	19
Leasing income	39	48
Total operating revenue	58	67
Variable lease income	25	34
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	19	19
Operating Segments | EnerBank
Disaggregation of Revenue [Line Items]
Financing income	62	49
Total operating revenue	62	49
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,025	1,100
Financing income	3	3
Total operating revenue	1,028	1,103
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	481	523
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	339	351
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	140	162
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	65	64
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	714	838
Financing income	2	2
Total operating revenue	716	840
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	493	589
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	149	174
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	20	25
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	52	50
Operating Segments | Consumers Energy Company | Enterprises
Disaggregation of Revenue [Line Items]
Total operating revenue	0	0
Operating Segments | Consumers Energy Company | EnerBank
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 0	$ 0