Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,864	$ 2,059
Net income	243	213
Plant, property, and equipment, gross	25,675		$ 25,390
Total Assets	27,447		26,837
Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,744	1,943
Net income	235	226
Plant, property, and equipment, gross	25,246		24,963
Total Assets	24,206		23,699
Operating Segments | Electric Utility
Segment Reporting Information [Line Items]
Operating Revenue	1,028	1,103
Net income	118	105
Plant, property, and equipment, gross	16,338		16,158
Total Assets	15,397		14,911
Operating Segments | Electric Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,028	1,103
Net income	118	105
Plant, property, and equipment, gross	16,338		16,158
Total Assets	15,459		14,973
Operating Segments | Gas Utility
Segment Reporting Information [Line Items]
Operating Revenue	716	840
Net income	117	121
Plant, property, and equipment, gross	8,887		8,785
Total Assets	8,678		8,659
Operating Segments | Gas Utility | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	716	840
Net income	117	121
Plant, property, and equipment, gross	8,887		8,785
Total Assets	8,725		8,706
Operating Segments | Enterprises
Segment Reporting Information [Line Items]
Operating Revenue	58	67
Net income	20	7
Plant, property, and equipment, gross	407		405
Total Assets	553		527
Operating Segments | Enterprises | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	0	0
Operating Segments | EnerBank
Segment Reporting Information [Line Items]
Operating Revenue	62	49
Net income	14	11
Plant, property, and equipment, gross	22		22
Total Assets	2,640		2,692
Operating Segments | EnerBank | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	0	0
Other reconciling items
Segment Reporting Information [Line Items]
Net income	(26)	$ (31)
Plant, property, and equipment, gross	21		20
Total Assets	179		48
Other reconciling items | Consumers Energy Company
Segment Reporting Information [Line Items]
Plant, property, and equipment, gross	21		20
Total Assets	$ 22		$ 20