Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Operating Revenue	$ 2,083	$ 1,864
Net income available to common stockholders	349	243
Plant, property, and equipment, gross	28,457		$ 27,907
Assets	29,723		29,666
Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,937	1,744
Net income available to common stockholders	336	235
Plant, property, and equipment, gross	27,299		26,757
Assets	25,280		25,399
Other reconciling items
Segment Reporting Information [Line Items]
Net income available to common stockholders	(34)	(26)
Plant, property, and equipment, gross	22		21
Assets	225		23
Other reconciling items | Consumers Energy Company
Segment Reporting Information [Line Items]
Plant, property, and equipment, gross	22		21
Assets	19		29
Electric Utility | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	1,134	1,028
Net income available to common stockholders	155	118
Plant, property, and equipment, gross	17,574		17,155
Assets	15,906		15,829
Electric Utility | Operating Segments | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	1,134	1,028
Net income available to common stockholders	155	118
Plant, property, and equipment, gross	17,574		17,155
Assets	15,969		15,893
Gas Utility | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	803	716
Net income available to common stockholders	181	117
Plant, property, and equipment, gross	9,703		9,581
Assets	9,244		9,429
Gas Utility | Operating Segments | Consumers Energy Company
Segment Reporting Information [Line Items]
Operating Revenue	803	716
Net income available to common stockholders	181	117
Plant, property, and equipment, gross	9,703		9,581
Assets	9,292		9,477
Enterprises | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	76	58
Net income available to common stockholders	14	20
Plant, property, and equipment, gross	1,118		1,113
Assets	1,275		1,276
EnerBank | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenue	70	62
Net income available to common stockholders	33	$ 14
Plant, property, and equipment, gross	40		37
Assets	$ 3,073		$ 3,109