Revenue (Components Of Operating Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	$ 1,347	$ 1,413	$ 3,304	$ 3,286
Leasing income	42		90
Leasing income		37		76
Financing income	56	40	110	79
Alternative revenue programs		2		4
Total operating revenue	1,445	1,492	3,504	3,445
Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	16	24	35	48
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,331	1,389	3,269	3,238
Financing income	3	4	8	8
Alternative revenue programs		2		4
Total operating revenue	1,334	1,395	3,277	3,250
Consumers Energy Company | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	621	669	1,733	1,707
Consumers Energy Company | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	420	444	945	967
Consumers Energy Company | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	182	179	369	346
Consumers Energy Company | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	108	97	222	218
Operating Segments | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,026	1,087	2,126	2,163
Financing income	1	2	4	4
Total operating revenue	1,027	1,089	2,130	2,167
Operating Segments | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	305	302	1,143	1,075
Financing income	2	2	4	4
Alternative revenue programs		2		4
Total operating revenue	307	306	1,147	1,083
Operating Segments | Enterprises
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	16	24	35	48
Leasing income	42		90
Leasing income		37		76
Total operating revenue	58	61	125	124
Operating Segments | Enterprises | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	16	24	35	48
Operating Segments | Consumers Energy Company | Electric Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	1,026	1,087	2,126	2,163
Financing income	1	2	4	4
Total operating revenue	1,027	1,089	2,130	2,167
Operating Segments | Consumers Energy Company | Electric Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	423	475	946	976
Operating Segments | Consumers Energy Company | Electric Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	362	386	713	747
Operating Segments | Consumers Energy Company | Electric Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	174	170	336	313
Operating Segments | Consumers Energy Company | Electric Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	67	56	131	127
Operating Segments | Consumers Energy Company | Gas Utility
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	305	302	1,143	1,075
Financing income	2	2	4	4
Alternative revenue programs		2		4
Total operating revenue	307	306	1,147	1,083
Operating Segments | Consumers Energy Company | Gas Utility | Residential
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	198	194	787	731
Operating Segments | Consumers Energy Company | Gas Utility | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	58	58	232	220
Operating Segments | Consumers Energy Company | Gas Utility | Industrial
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	8	9	33	33
Operating Segments | Consumers Energy Company | Gas Utility | Other
Disaggregation of Revenue [Line Items]
Revenue recognized from contracts with customers	41	41	91	91
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	53	36	102	71
Total operating revenue	53	36	102	71
Other reconciling items | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Total operating revenue	$ 0	$ 0	$ 0	$ 0