Revenue (Components of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,671	$ 1,468	$ 5,148	$ 4,569
Leasing income	50	36	136	110
Financing income	3	3	11	12
Consumers alternative-revenue programs			1
Total operating revenue	1,725	1,507	5,296	4,691
Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,416	1,255	3,705	3,300
Financing income	2	2	7	7
Consumers alternative-revenue programs			1
Total operating revenue	1,419	1,257	3,713	3,307
Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	224	192	1,357	1,212
Financing income	1	1	4	5
Consumers alternative-revenue programs			0
Total operating revenue	225	193	1,361	1,217
Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	31	21	86	57
Leasing income	50	36	136	110
Total operating revenue	81	57	222	167
Variable lease income	35	23	94	69
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,640	1,447	5,062	4,512
Financing income	3	3	11	12
Consumers alternative-revenue programs	1		1
Total operating revenue	1,644	1,450	5,074	4,524
Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,416	1,255	3,705	3,300
Financing income	2	2	7	7
Consumers alternative-revenue programs	1		1
Total operating revenue	1,419	1,257	3,713	3,307
Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	224	192	1,357	1,212
Financing income	1	1	4	5
Consumers alternative-revenue programs	0		0
Total operating revenue	225	193	1,361	1,217
Residential | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	861	744	2,764	2,431
Residential | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	718	624	1,847	1,612
Residential | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	143	120	917	819
Commercial | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	492	440	1,449	1,320
Commercial | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	456	413	1,191	1,093
Commercial | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	36	27	258	227
Industrial | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	172	166	494	459
Industrial | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	167	161	458	427
Industrial | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	5	5	36	32
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	31	21	86	57
Other | Enterprises | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	31	21	86	57
Other | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	115	97	355	302
Other | Consumers Energy Company | Electric Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	75	57	209	168
Other | Consumers Energy Company | Gas Utility | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 40	$ 40	$ 146	$ 134