Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,443	$ 1,445	$ 3,307	$ 3,504
Net income (loss) available to common stockholders	136	93	379	306
Plant, property, and equipment, gross	25,911		25,911		$ 25,390
Total Assets	28,581		28,581		26,837
Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,330	1,334	3,074	3,277
Net income (loss) available to common stockholder	159	97	394	323
Plant, property, and equipment, gross	25,468		25,468		24,963
Total Assets	25,060		25,060		23,699
Operating Segments | Electric Utility
Segment Reporting Information [Line Items]
Operating Revenue	1,022	1,027	2,050	2,130
Net income (loss) available to common stockholders	119	90	237	195
Plant, property, and equipment, gross	16,447		16,447		16,158
Total Assets	15,925		15,925		14,911
Operating Segments | Electric Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,022	1,027	2,050	2,130
Net income (loss) available to common stockholder	119	90	237	195
Plant, property, and equipment, gross	16,447		16,447		16,158
Total Assets	15,987		15,987		14,973
Operating Segments | Gas Utility
Segment Reporting Information [Line Items]
Operating Revenue	308	307	1,024	1,147
Net income (loss) available to common stockholders	41	8	158	129
Plant, property, and equipment, gross	9,001		9,001		8,785
Total Assets	9,006		9,006		8,659
Operating Segments | Gas Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	308	307	1,024	1,147
Net income (loss) available to common stockholder	41	8	158	129
Plant, property, and equipment, gross	9,001		9,001		8,785
Total Assets	9,052		9,052		8,706
Operating Segments | Enterprises
Segment Reporting Information [Line Items]
Operating Revenue	52	58	110	125
Net income (loss) available to common stockholders	1	16	21	23
Plant, property, and equipment, gross	408		408		405
Total Assets	542		542		527
Operating Segments | EnerBank
Segment Reporting Information [Line Items]
Operating Revenue	61	53	123	102
Net income (loss) available to common stockholders	8	10	22	21
Plant, property, and equipment, gross	35		35		22
Total Assets	2,799		2,799		2,692
Other reconciling items
Segment Reporting Information [Line Items]
Net income (loss) available to common stockholders	(33)	(31)	(59)	(62)
Plant, property, and equipment, gross	20		20		20
Total Assets	309		309		48
Other reconciling items | Consumers Energy Company
Segment Reporting Information [Line Items]
Net income (loss) available to common stockholder	(1)	$ (1)	(1)	$ (1)
Plant, property, and equipment, gross	20		20		20
Total Assets	$ 21		$ 21		$ 20