Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,442	$ 1,519	$ 4,746	$ 4,805
Leasing income	42		132
Leasing income		36		112
Financing income	62	43	172	122
Alternative revenue programs		1		5
Total operating revenue	1,546	1,599	5,050	5,044
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	17	21	52	69
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,425	1,498	4,694	4,736
Financing income	4	3	12	11
Alternative revenue programs		1		5
Total operating revenue	1,429	1,502	4,706	4,752
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	696	743	2,429	2,450
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	454	464	1,399	1,431
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	178	190	547	536
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	97	101	319	319
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,247	1,310	3,373	3,473
Financing income	3	3	7	7
Total operating revenue	1,250	1,313	3,380	3,480
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	178	188	1,321	1,263
Financing income	1	0	5	4
Alternative revenue programs		1		5
Total operating revenue	179	189	1,326	1,272
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	17	21	52	69
Leasing income	42		132
Leasing income		36		112
Total operating revenue	59	57	184	181
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	17	21	52	69
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,247	1,310	3,373	3,473
Financing income	3	3	7	7
Total operating revenue	1,250	1,313	3,380	3,480
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	585	625	1,531	1,601
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	427	434	1,140	1,181
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	175	186	511	499
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	60	65	191	192
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	178	188	1,321	1,263
Financing income	1	0	5	4
Alternative revenue programs		1		5
Total operating revenue	179	189	1,326	1,272
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	111	118	898	849
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	27	30	259	250
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	3	4	36	37
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	37	36	128	127
Operating Segments | Consumers Energy Company | Enterprises
Disaggregation of Revenue [Line Items]
Total operating revenue	0	0	0	0
Other reconciling items
Disaggregation of Revenue [Line Items]
Financing income	58	40	160	111
Total operating revenue	58	40	160	111
Other reconciling items | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 0	$ 0	$ 0	$ 0