Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenue	$ 1,558	$ 1,382	$ 3,571	$ 3,184
Net income available to common stockholders	176	136	525	379
Plant, property, and equipment, gross	29,027		29,027		$ 27,870
Assets	29,953		29,953		29,666
Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,493	1,330	3,430	3,074
Net income available to common stockholders	189	159	525	394
Plant, property, and equipment, gross	27,910		27,910		26,757
Assets	25,680		25,680		25,399
Other reconciling items
Segment Reporting Information [Line Items]
Net income available to common stockholders	(19)	(25)	(20)	(37)
Plant, property, and equipment, gross	22		22		21
Assets	3,139		3,139		3,132
Other reconciling items | Consumers Energy Company
Segment Reporting Information [Line Items]
Net income available to common stockholders	(1)	(1)	(1)	(1)
Plant, property, and equipment, gross	22		22		21
Assets	21		21		29
Electric Utility | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	1,160	1,022	2,294	2,050
Net income available to common stockholders	154	119	309	237
Plant, property, and equipment, gross	17,816		17,816		17,155
Assets	16,078		16,078		15,829
Electric Utility | Operating Segments | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,160	1,022	2,294	2,050
Net income available to common stockholders	154	119	309	237
Plant, property, and equipment, gross	17,816		17,816		17,155
Assets	16,141		16,141		15,893
Gas Utility | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	333	308	1,136	1,024
Net income available to common stockholders	36	41	217	158
Plant, property, and equipment, gross	10,072		10,072		9,581
Assets	9,470		9,470		9,429
Gas Utility | Operating Segments | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	333	308	1,136	1,024
Net income available to common stockholders	36	41	217	158
Plant, property, and equipment, gross	10,072		10,072		9,581
Assets	9,518		9,518		9,477
Enterprises | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	65	52	141	110
Net income available to common stockholders	5	$ 1	19	$ 21
Plant, property, and equipment, gross	1,117		1,117		1,113
Assets	$ 1,266		$ 1,266		$ 1,276