Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,343	$ 1,347	$ 3,101	$ 3,304
Leasing income	35	42	74	90
Financing income	65	56	132	110
Total operating revenue	1,443	1,445	3,307	3,504
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	17	16	36	35
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,326	1,331	3,065	3,269
Financing income	4	3	9	8
Total operating revenue	1,330	1,334	3,074	3,277
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	713	621	1,687	1,733
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	392	420	880	945
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	133	182	293	369
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	88	108	205	222
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,020	1,026	2,045	2,126
Financing income	2	1	5	4
Total operating revenue	1,022	1,027	2,050	2,130
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	306	305	1,020	1,143
Financing income	2	2	4	4
Total operating revenue	308	307	1,024	1,147
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	17	16	36	35
Leasing income	35	42	74	90
Total operating revenue	52	58	110	125
Variable lease income	21	29	46	63
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	17	16	36	35
Operating Segments | EnerBank
Disaggregation of Revenue [Line Items]
Financing income	61	53	123	102
Total operating revenue	61	53	123	102
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,020	1,026	2,045	2,126
Financing income	2	1	5	4
Total operating revenue	1,022	1,027	2,050	2,130
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	507	423	988	946
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	341	362	680	713
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	126	174	266	336
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	46	67	111	131
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	306	305	1,020	1,143
Financing income	2	2	4	4
Total operating revenue	308	307	1,024	1,147
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	206	198	699	787
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	51	58	200	232
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	7	8	27	33
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 42	$ 41	$ 94	$ 91