Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,957	$ 1,873
Leasing income	48
Leasing income		39
Financing income	54	39
Alternative revenue programs	0	2
Total operating revenue	2,059	1,953
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	19	24
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,938	1,849
Financing income	5	4
Alternative revenue programs	0	2
Total operating revenue	1,943	1,855
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,112	1,038
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	525	523
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	187	167
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	114	121
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,100	1,076
Financing income	3	2
Total operating revenue	1,103	1,078
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	838	773
Financing income	2	2
Alternative revenue programs	0	2
Total operating revenue	840	777
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	19	24
Leasing income	48
Leasing income		39
Total operating revenue	67	63
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	19	24
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,100	1,076
Financing income	3	2
Total operating revenue	1,103	1,078
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	523	501
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	351	361
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	162	143
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	64	71
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	838	773
Financing income	2	2
Alternative revenue programs	0	2
Total operating revenue	840	777
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	589	537
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	174	162
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	25	24
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	50	50
Operating Segments | Consumers Energy Company | Enterprises
Disaggregation of Revenue [Line Items]
Total operating revenue	0	0
Other reconciling items
Disaggregation of Revenue [Line Items]
Financing income	49	35
Total operating revenue	49	35
Other reconciling items | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 0	$ 0