Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,468	$ 1,442	$ 4,569	$ 4,746
Leasing income	36	42	110	132
Financing income	71	62	203	172
Total operating revenue	1,575	1,546	4,882	5,050
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	21	17	57	52
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,447	1,425	4,512	4,694
Financing income	3	4	12	12
Total operating revenue	1,450	1,429	4,524	4,706
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	744	696	2,431	2,429
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	440	454	1,320	1,399
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	166	178	459	547
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	97	97	302	319
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,255	1,247	3,300	3,373
Financing income	2	3	7	7
Total operating revenue	1,257	1,250	3,307	3,380
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	192	178	1,212	1,321
Financing income	1	1	5	5
Total operating revenue	193	179	1,217	1,326
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	21	17	57	52
Leasing income	36	42	110	132
Total operating revenue	57	59	167	184
Variable lease income	23	28	69	91
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	21	17	57	52
Operating Segments | EnerBank
Disaggregation of Revenue [Line Items]
Financing income	68	58	191	160
Total operating revenue	68	58	191	160
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,255	1,247	3,300	3,373
Financing income	2	3	7	7
Total operating revenue	1,257	1,250	3,307	3,380
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	624	585	1,612	1,531
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	413	427	1,093	1,140
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	161	175	427	511
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	57	60	168	191
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	192	178	1,212	1,321
Financing income	1	1	5	5
Total operating revenue	193	179	1,217	1,326
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	120	111	819	898
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	27	27	227	259
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	5	3	32	36
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 40	$ 37	$ 134	$ 128